FORTHE PEOPLE FOR EDVCATION FORSCIENCE LIBRARY OF THE AMERICAN MUSEUM OF NATURAL HISTORY , i*^ "^ NATURE SKETCHES IN TEMPERATE AMERICA "Stranger, if thou hast learned a truth wliieh needs no school of long experi- ence, that tiic world is full of guilt and misery, and hast seen enough of all its sorrows, crimes, and cares, to tire thee of it, enter this wild wood and view the haunts of nature." Bryant. From "Entrance to a \Voo Post-Darwinian questions in "Darwin and After Darwin," Part III, p. 2. Plant and Insect Association of the Meadow in Sf.ptemker Tlie blazing star {Lacinaria spicata) xcith its insect visitors, the butterfly {Argynnis bellona) , and the clear-xcing moth (Hcmaris axilhtris) . From a photograph ADAPTATIONS IN ANIMALS AND PLANTS 29 their bodies unaffected. These seeds are favored in their germination by the heat and moisture to which they have been subjected, and perhaps later derive nourishment from the excreta passed with them. The fruits bearing the seeds often possess bright colors as they ripen and are charged with agree- ably tasting juices which render them edible to animals. Some of these fruits are poisonous to some animals, but harmless to others. The bright orange mountain-ash berries are much enjoyed by the common waxwing; the black elderberries are consumed by several species of birds; and Wallace states that there is probably nowhere a brightly colored pulpy fruit which does not serve as a food for some species of bird or mammal. The drupes of the poison ivy are freely devoured by crows and in this way the plant is widely disseminated in our woods. While the seeds are often dispersed as above described, it is an interesting fact, as Grant Allen has mentioned, that the fruits of our forest trees are protected during their develop- ment. At this time they are green when on the tree and hardly visible among the foliage, but as they ripen they turn brown and fall to the ground. Such, for instance, are the beech, butter- nuts, chestnuts, and the walnuts. The beechnuts and chestnuts are provided with a prickly coat that protects them to some extent, while the butternuts and walnuts have an acrid, pungent covering before they are ripe. I have seen young red squirrels eat nearly ripe beech and butternuts, biting through and discarding the outer covering. Out of the enormous cjuantities of these nuts that are produced some are doubtless able to propagate and produce young trees. The wild pigeons that formerly ranged over North America in such enormous flocks fed on acorns, which they swallowed whole without bruising, and these were digested and used up in nutriment. Squirrels and gophers are fond of acorns, and these nuts are destroyed by the acorn weevil, yet with all the great number of them consumed, there are enough produced that some of them find favorable places for germination and growth. The smaller plants, such as grasses, sedges, composites, and umbelliferas, drop their seeds directly to the ground, and these have obscurely colored capsules and small brown seeds. Plants, 30 NATURE SKETCHES IN TEMPERATE AMERICA such as the wild columbine, eject their small seeds by the burst- ing open of their capsules. Wallace intimates a suggestive fact that dominant groups of our large forest trees, such as oaks and beeches, are among the most ancient of known dicotyledonous plants, going back to the cretaceous period with little change of type, so that it is not improbable that they may be older than any fruit-eating mammal adapted to feed upon their fruits. The attractive colored fruits, according to Grant Allen, on the other hand, having so many special adaptations to dispersal by birds and manmials, are probably of more recent origin. Wallace maintains, "The apple and the plum tribes are not known earlier than the miocene period; and although the record of extinct vegetable life is extremely imperfect, and the real antitjuity of these groups is no doubt very much greater, it is not improbable that the comparative antiquity of the fruit-bearing and nut-bearing trees may remain unchanged by further discoveries, as has almost always hapi)ened as regards the comparative antiquity of animal groups." At the present time adaptation "is precisely one of the things evolutionists are trying to find the causes or causal factors of. But nevertheless the adaptability of life stuflF, its plasticity and capacity of advantageous reaction, is, to many biologists, a fundamental fact in organic nature, like gravitation or chemical affinity in organic nature; a thing basic and inexj)lirable, and in itself a factor whose consequences are to be determined but not further to be questioned as to their cause." ' Flower and Insect Adaptations Lubbock says that "not only have the form and colors, the bright tints, the sweet odors, and the nectar been gradually developed by the force of an unconscious selection exercised by insects, but even the arrangement of colors, the shape, the size, and the position of the petals, the relative position of the stamens and pistil are all determined by the visits of the insects, and in such a way as to assure the great object (fertilization) that these visits are intended to effect." ' Jordan and Kellogg, " Evolution and Animal Life," p. 56. ADAPTATIONS IN ANIMALS AND PLANTS 31 Many facts have been brought forward to prove that this relation actually exists, but not entirely on the assumption laid down by Lubbock. Recent studies by Bouvier, on the "Relation of Bees to Flowers," are summarized as follows: Nectar and nectaries are certainly intended primarily for the plant itself and do not prove an adaptation of the flower to insects. The colors and perfumes of flowers may be, perhaps, the result of such an adaptation, but in any case they strongly attract anthrophilian insects, signalling to them the presence of booty. In many cases, if not all, the complicated forms of the flowers must be attributed to the adaptation of flowers to their visits. It is almost unanimously conceded nowadays that Mellifera (or bees), at least in so far as their collecting apparatus is concerned, are beautifully adapted to the flowers, but, despite the fact that practice has shown that plants are in every way more plastic than animals, it is still strongly disputed that flowering plants have adapted themselves to bees. "If there does not exist any reciprocal modification," says Bouvier, "between the Mellifera (bees) and the flowering plants, it is not at all necessary to suppose that one group has been modified for the benefit of the other. Each has evolved on its own account." Explained thus, the many objections to the theory of reciprocal adaptation are overthrown. The bee has but one object, the pursuit of food, and all things which aid him in it are welcome. Usually, the plant profits thereby; sometimes it suffers. On the other hand, the plant seeks only to assure its propagation and all its modifications tend toward that goal. M. Gaston Bonnier quotes Claude Bernard as saying, "The law of the physiological finality is in each indi- vidual being and not outside it; the living organism is made for itself; it has its own intrinsic laws. It works for itself and not for others." Darwin, IMiiller, Lubbock, as well as others, have written detailed accounts of the adaptations of flowers to insects.^ During the visits of insects to flowers for the purpose of obtain- ing secretions of nectar and pollen, they involuntarily carry the pollen of one flower to the stigma of another, and thus ^ For a discussion of this subject consult Wallace, " Natural Selection and Tropical Nature," p. -400. 32 NATURE SKETCHES IX TEMPERATE AMERICA effect cross-fertilization. Darwin was the first to demonstrate that the vigor and fertihty of the next generation of plants w^ere greatly increased by this process. It was, moreover, this discovery that led to researches which disclosed the most wonderful and complex arrangements that exist in flowers, all having for their object the prevention of constant self- fertihzation; but that pollen shall be carried, either constantly or occasionally, from the flowers of one plant to those of another. There was thus established the fact that the arrangement, length, and position of all the parts of the flower have a definite purpose, though a great variety of ways exist by which this same result is obtained. Open cup-shaped and quite regular flowers, in which it seems inevitable that the pollen must fall on the stigma and produce constant self-fertilization, are often prevented from doing so by a physiological variation. In these cases the anthers, continually emitting their pollen, wither either a little earlier or a little later than the stigmas of the same flower or of other flowers on the same })lant when in the best state to receive it. As individual plants differ somewhat in the time of flowering, the pollen of one plant would often be conveyed by insects to some other plant whose stigmas were in a proper condition to be fertilized by it. Variations occurred in first one part, then in another, which have resulted in various adaptations for insect fertilization. Odors are developed as an attraction or guide to insect fertili- zation. Inconspicuous flowers are often possessed of strong, sweet odors, to be detected some distance away, while very showy flowers are seldom thus provided with scents. White flowers are usualh' exceedingly sweet perfumed. They are mostly fertilized by night-flying moths. The grouping of flowers so that they attract insects is often of considerable advantage. They are often conspicuously dis- played in a broad flat top, such as is exhibited in the elderberry and wild carrot. These groups are made up of many individual flowers. Then there is the grouping shown in those of the lilacs and horse-chestnut. Again, we witness them closely packed together in tiny florets forming dense heads, as in the clover and all the Compositae, and in these the marginal florets are modified into rays such as shown in the daisy, aster. ADAPTATIONS IN ANIMALS AND PLANTS 33 and sunflower. Bees are much more of a factor in fertiliza- tion in the temperate zone than butterflies. It is a general rule that flowers fertilized by the latter are much more con- spicuous than those fertilized by bees. It is generally the case that the time of blossoming of these plants corre- sponds with the appearance of certain insects and in a few cases adjusted to the time of arrival of the ruby-throated humming-bird. It has that "arctic flowers be colored in proportion ^ • of winter, insects ^j eration in the act more uncertain been asserted by Grisebach come larger and more richly as, by the increasing length become rarer, and their coiip- of fecundation is exposed to chances." ^ Why the Nectar Gatherers Assemble on the Bass- wood Blossoms .N a warm sunn}' day in the middle of July, the linden tree in blossom affords a centre of attraction for many insects. The sweet perfumed blossoms are scented far and wide by a host of busy httle wanderers that come and congregate there. Such insects as the bumble and the honey bees are seen hanging to the pendent flower clusters, drink- ing the honey, while on the sur- face of the leaves many small flies play in the sunshine, and now and then take their lunch from the flowers. Ar- gynnid and skipper butter- flies participate in the grand Species of bees, flies, and wasps collectively fly out into mid-air about the blossoms at every stir of the limbs and foliage. The birds, too, become aware of this meeting convention of life. 'Wallace, in "Natural Selection and Tropical Nature," p. 407. 34 NATURE SKETCHES IN TEMPERATE AMERICA ground, and while viewing these sights, a Baltimore oriole snaps at some selected winged morsel. Like the mulberry tree in its attraction for birds, so the linden tree, in full blossom, is a delight to the senses of insect life, causing them to divide their attention between it, the chestnut, and the elderberry, which all blossom at the same time. Near one of the large basswood trees, where a view may be gained into its upper branches, the floral display alone, with its treat of perfume, is sufficient attrac- tion; but, coupled with the harvest of insect visitors, one may easily spend a profitable hour contemplating the wonderful view, and adding something to the meaning of this great activity. On examining the flowers of the basswood, the honey is found secreted and held in the hollow sepals. "The petals and sepals are overtopped by the numerous stamens which curve outward so that insects can only alight on the anthers, or on the stigmas and the space between them. The possibility of self-fertilization is almost excluded by the stamens remaining bent outward to the last, while the pistil occupies the axis of the flower; only rarely is a flower met with in which an anther has become curved inward to touch the stigma." ' The honey is only accessible to insects with short tongues. As none of the bees visiting the basswood blossoms had pollen in their baskets, Miiller concluded that these insects visited the flowers for the honey and not for the pollen. There is an explanation of the cause of the diverse forms of insect frequenters to the basswood blossoms if we remember the observations of Knuth: "First, the more specialized a flower — i.e., the more complex its structural arrangements and the more deeply seated its nectar — the less are its insect visitors indiscriminately drawn from the entire insect faima of a district, and the more do they belong to one or several similar species adapted to pollination. Secondly, the flatter and more superficial the position of the nectar, the more varied are the visitors in (lifl"orent regions, and the more are they indiscriminately drawn from the entire insect faima of the region in question." - The basswood blossoms, shown in the plate illustration, * Miiller, "Fertilization of Flowers," p. 14G. '"Handbook," Vol. I. 1906, p. 196. ADAPTATIONS IN ANIMALS AND PLANTS 35 Insect Visitors to the Basstvood Blossoms (Tilia americana). The insect on thefloicer to the right is a honey bee; the one to the left and the one flying are Syrphus flies {Sphaerophoria cylindrica). The lower itisect is a small beetle flying. 36 NATURE SKETCHES IX TEMPERATE AMERICA have the nectar shallowly held in the hollow sepals accessible to a great variety of insect guests. The scent of these flowers is perceived for a distance of several hundred yards ; the paraffin- oids composing it have the peculiar property of increasing in intensity the farther away the perfume floats on the air up to a certain distance, when it finally disperses by diffusion through the air. In view of these facts, it is not difficult to perceive why the nectar gatherers have preference for the basswood flowers. How THE Milkweed Profits by the Visits gf its Insect Guests N another chapter on the Monarch Butter- fly and its Mimic, I will refer to the familiar banded larva found on the milk- weed. On this plant are also found cer- tain other insects. One can hardly think of the greenish purple umbels of the conunon milkweed without associating with these exquisitely perfumed flowers the red, four-sjiotted beetle, Tetraopes tctra- ophthalmus. This snuill beetle, which has blackish antennae, is often seen in July resting on the leaves, singly or in pairs, as depicted in the colored plate (facing page 36). On sun- shiny days it is also seen flying from one plant to another. The life of this insect is intimately connected with the milkweed, the roots and lower parts of the stems of this plant furnishing nutrition for the larvae which penetrate and feed upon them. Besides the almost constant presence of the red, four-spotted beetle, the perfumed flowers entice winged insects of many kinds. These include such forms as bees, wasps, flies, butter- flies, moths, beetles, and occasionally bugs. Guided by the scent, the insects are easily led to the honey. But while the insects are in quest of this food, there is a reciprocal process between plant and guest. At the same time they visit the flowers they perform pollination, which is of great importance to the plant's perpetuation. The dependence of these plants ujKin insects as agents for transferring pollen is shown by the peculiar structure of the flowers, many of them Insect Visitors to the Milkweed {Axc/epids cormifi) The iii.sectx (ire the red-spotted beetles {Tel mopes telraopthtihuKs) , xchose lives are intimately associated icith this plant. From a photograph ADAPTATIONS IN ANIMALS AND PLANTS 37 The Sivamp Milkweed (Asclepias incarnata). It appears at the borders of ponds and swamps, lending color to these surroundings. 38 NATURE SKETCHES IN TEMPERATE AMERICA being as interesting in their adaptation to insect visitors as are the remarkable orchids. A more minute examination shows that the purple flower has the corolla deeply divided into five parts. Next to the corolla is a crown of five spreading hoods, each bearing within a slender incurved horn. The five stamens are attached to the corolla; the filaments are joined into a tube enclosing the pistil. The anthers are joined to the stigma and flexed inward and winged, broadening below the middle; and between these anther wings is a .slit — the stigmatic chamber. This fissure is bridged above by the pollen-bearing organ known as the corpusculum. The latter may be compared to a wish-bone in shape; each flattened side is called a pollinia and forms part of two neighboring anthers. The upper part is formed into a wedge-shaped slit. One of the corpuscula lies within each of the five slits of the crown. ()])j)osite the anthers there are five fleshy, leaf-like organs whith secrete a large (juantity of honey. Miiller says: ''When insects creep about the umbels in search of honey, attracted by the sweet .scent of the flowers, they slip upon the smooth parts of the flower until a foot enters the wide inferior part of the slit, in which it gets a firm hold. When the in.sect tries to draw its foot out in order to proceed farther, the diverging claws are caught by the opposed edges of the anther wings and guided upward in the slit, so that one or the other of the two claws is brought without fail into the notch in the lower border of the corpusculum and there held fast. If the insect now draws its foot forcibly out, it brings with it the corpusculum and two j)ollinia attached to it by their reti- nacula. The pollinia stand wide apart when they are extracted, but the retinacula twist upward as they dry, bringing the l)()llinia so close together that they nuiy easily lie introduced into another slit. As the insect moves over the umbel, its foot, bearing the pollinia, sli])s into the lower part of a slit of another flower; and this time, as the leg is drawn up, the pollinia are left in the stigmatic chamber opposite to the stigma, since the slit is too narrow to admit of their further passage upward, and the insect, freeing its foot by a violent pull, snaps the retinacula and so extricates itself. The pollinia are left behind ADAPTATIONS IN ANIMALS AND PLANTS 39 in the stigmatic chamber while the corpusculum and its broken retinacula are carried off, still firmly attached to the insect's foot. The insect continues its visits and the retinacula at- tached to its feet now get fixed in corpuscula as the claws did before, and the insect's foot, after repeated visits, may some- times be seen bearing corpuscula with their retinacula often dichotomously arranged."^ While the pollinia of the common milkweed is frequently attached to the claws of insects and rarely to the hairs and mouth parts, in the allied species of milkweed, A. verticillata, the pollinia are usually attached to the hairs of insect visitors. The peculiar structure of the milkweed flowers is such that small, weak insects are often entrapped and lose their lives by getting their feet entangled in the pollen masses or caught in the slits of the crown, from which they are unable to release them. I have found numbers of dead house flies on some of the flowers of the common milkweed, which had been too weak to extricate their feet from the slits. Similarly, on other occa- sions, I have found honey bees and Syrphus flies which had been held captive in the same way. Among unbidden guests of the common milkweed, ants are frequently seen, especially the larger, dark-colored species. At certain times I have seen them swarming over the stems and flowers. The species of swamp milkweed, A. incarnata, shown in the illustration, is easily distinguished from the common milkweed species. The dull crimson pink blossoms appear from July to September. It is fertilized by bees and bee-like flies and will be found full of interest when studied from the standpoint of its insect visitors acting as fertilizers of the flowers. It is also found at the border of ponds and in wet meadows. The common milkweed, on the other hand, grows in great luxuriance on dry, sandy ground. * " Fertilization of Flowers," p. 398. 40 NATURE SKETCHES IN TEMPERATE AMERICA viUic'5^^ The Selected Guests of J'iiiW.j \r?;''%,) THE BCTTERFLY WeED U-. 1^ >*:£i»- ^ *- > •rn ^ ^ 1 HOW l>rilliant '\ llie flowers of the orange huttordy weed appear in the field, when viewed in the bright sun of a July day! Under these conditions they show with a splendor only known to the flowers of this species. Not only the rich color of the blossoms appear to have charms for insect guests, but the pollen and sweets seem to meet their most exacting whims. A veritable entomological garden is spread before us as we approach. \'arious winged insects, from butterflies to small flies, are all busily occupied among the blossoms. Nearby are half-opened flowers of the goldenrod and the pretty, scented, lace-like flowers of the wild carrot, but they are for the moment completely ignored by these special insect guests. I have alreatly considered the structure of the blossoms of the common milkweed and have endeavored to show how the delicate and weaker flies and bees sometimes fall victims by having their feet entangled in the pollen masses of the flowers. These pollen organs or corpuscula become clasped, as if animated, to the feet of certain insects. Some of the weaker insects are unable to disentangle themselves, and these captives either die of exhaustion or fall prey to the ants, which often swarm upon these plants. The larger insects, such as the wasps, ADAPTATIONS IN ANIMALS AND PLANTS 41 make their escape, carrying away the poUinia, which they trans- port to other blossoms during their visits. In this way they bring the pollen in contact with the stigma, and thus fertilize the flowers. But the butterfly weed differs from the common milkweed in possessing the allurements of brilliant color, though without fragrance. The weaker insects that frequent these blossoms are not destroyed in such numbers. To the butterflies, the floral spread presents an enticing playground, as well as a place to bancjuet. And even the weak flies and small bugs move about among the bright flowers with impunity. But upon one wasp, Ammophila, and sev- eral bees, Bombus, the butterfly weed unconscioush' enforces the more serious burden of Uterally compelling the trans- fer of pollen. WTien I carried this inquiry a little further, one day, by sweeping the insects one by one into my net, I found in the general round-up the following representatives: one large, slender- waisted wasp, Ammophila; three Argynnid butterflies, Argynnis cyhele; one of the crescent-spot butterflies, Phyciodes thaws; one Ajax butterfly, a number of bees of the genus Bombus; several small, clear-wing flies, and two small bugs. On examination of their feet with a hand magnifier, the real pollen carriers were revealed at once. The wasp's feet had a number of the pollinia attached to the hairs at different parts of the tarsi, while the bees' feet were fairly loaded with them. But as to the rest of the insects enumerated, I found their feet entirely free from pollinije, they having escaped the pollinia traps set only for the larger forms that I have mentioned. WTien finding the butterfly weed on some bright day, let the reader stop and meditate, and study the insect visitors, before thinking of recklessly picking these exquisite flowers that adorn the outdoor landscape. Then let me hear from those who have made new additions to the list of these flower frequenters, which I have only suggested in my sketch. 42 NATURE SKETCHES IN TEMPERATE AMERICA f-V%^ Bird Flowers \ t^. J i//'i'' OW many times in passing through the I o w, wet meadows in May and June, have we stopped to I' j view the beautiful, painted cup flowers! But few of us f \ have pondered over the sig- nificance of their brilliant scar- let coloring. The fiowers will be recalled as having the corolla somewhat hidden by the long, two- lobed calyx, which is the part tipped with brilliant color. Then, too, the green I leaves are variously stained in the same vermilion or .scarlet, or, they may rarely be colored yellow. One day I was fortimate in coming on the .scene at the proper moment, to view the pretty little ruby-throated humming-bird, thirsting after his long flight, dart down to sip the nectar from .some of these blossoms. Only a short time previously I had .seen him poised in mid-air before the blossoms of the columbine, which grew in the opening near the woods. The preference this bird shows for these flowers has a far deeper meaning than appears on the surface. On a previous page, attention was called to the pollination of ADAPTATIONS IN ANIMALS AND PLANTS 43 flowers by insects, and here I have just witnessed the same phenomenon exhibited by the ruby-throat. If observations are carried further along in the season in July, August, and September, it will be found that certain flowers, such as the trumpet creeper, the spotted touch-me-not, and the cardinal flowers are really "bird flowers." In these flowers there is existing a reciprocal relation between the bird and flower, just as we have observed existing between flowers and insects. The following are the characteristic features of these bird flowers: they are erect in position; are either pouch-shaped or cylindrical in form; are noted for their brilliancy of color, generally either scarlet or yellow, and for the great amount of nectar that they secrete. In the tropics, they reach great perfection and variety of form, and in that latitude there exists coincidentally a great variety of humming-birds, with various elongated bills, to visit them. With us, there are fewer real bird flowers. These are all visited by the single species of humming-bird, the ruby- throat, that is found in summer over the whole temperate eastern North America. It proceeds north in the spring, during the vernal change in vegetation, and stays with us through the summer, and in the fall returns to the south. The migration of this species over such a vast extent of country is of particular interest in the present connection, for in carrying pollen from one flower to another situated widely apart, the cross-fertiliza- tion influence gives an impetus and strengthening character to the plants, as is well understood by students of plant breeding and was especially noted by Darwin. The relation between the ruby-throat and the period of blooming of bird flowers has received considerable attention by naturalists. Robinson suggests ^ that the spring and autumn migration of this bird may account for the tendency of these bird flowers to form an early and late group. Sprengel showed in his writings, in 1787, that he believed that the nectar of flowers is secreted for the sake of insects and is protected from rain in order that the insects may get it pure and unspoiled. Without going into details here, he was evidently the first, as Miiller believes, to "view the subject in the light of adapta- ^ American Naturalist, February, 1895, p. 113. 44 NATLTIE SKETCHES IN TEMPERATE AMERICA tion, and to show how all the colors, scents, and singular forms of flowers have some useful purpose." Sprengel made no mention of bird-pollination at the time of his writings, and overlooked the fact that some of these flowers are adapted more to birds than to insects. It is readily seen that a strictly specialized type of humming-bird, such as the foreign Hermit species, would fail to exist in our latitude. It is adapted to certain South American plants having the corolla often several inches in length. On the other hand, it was possible for a less differentiated bird type, with less specialized feeding habits, like our ruby- throated humming-bird, to succeed in establishing itself here. It is my opinion that insects were ])robably the first to visit flowers, but birds in search of these animals as food acquired a taste for the nectar, incidentally at first, and finally estal)lished an inherent taste for honey. Our own ruby-throat changes his diet from nectar to small sj;idors, or back again, according to the whim of his individual taste. AVhile insects that fre(|uent flowers often bear strictly specialized mouth parts in adaptation to their mode of life, the humming-bird's head and body appear to have been changed in accordance with his habits. Aside from the bill, which is modified in a remarkable manner, our ruby-throat bears unmistakable evidence of possessing devices which aid in the transference of pollen from one flower to another. The first account describing these structures I have published under the title of *'()rnitiioi)hilus Pollination" in the American Naturalist, 1804. Moreover, it is from this source I have abstracted the following account of the method by which this bird pollinizcs plants. "The common ruby-throated Ininuning-bird bears upon careful study evidence that the mouth parts and feathers have certain means for the harboring of pollen. The ana- tomical peculiarities of this bird's head allow access to flowers covering a wide range of forms. By reason of some flexibility, the bill is capable of probing to the bottom of nearly all the forms of flowers commonly met with. In the feeding process, familiar to almost every one, the flower is often l)ent over to be relieved of its juices. A cursory examination, with the naked eve, of this bird's head does not reveal with ADAPTATIONS IX ANIMALS AND PLANTS 45 Bill, Head, and Feathers oj Ruby-thruaied Humming-bird, showing how pollen of plants is carried. clear distinctness the main facts brought out by the use of a microscope, conse- quently, this instru- ment was brought into use in furthering research. Pollen is carried in several ways by this bird. On the lower mandible, just in front of the angle of the mouth, over- shadowed by the nasal scale when the bill is closed, a faint yellow- ish line usually marks the deposit of pollen grains resting in a small groove, clustered together, as shown in Fig. 5 at point b. Pollen grains work their way free to the summit or vanes of the feathers about where they were seen scat- tered, and, as will be described further on, caught up by the barbs of feathers, along the sides of the chin and lores ready to be deposited when a more suitable sur- face presents. Under the lower bill, as shown in enlarged view. Fig. 1, and also 46 NATURE SKETCHES IX TEMPERATE AMERICA 5a, the deep median groove, and the point of meeting of the rami, which traverses alone for nearly one-half its length, acts as a second repository. This pollen repository groove becomes divided backwards on either side for a short distance. Pollen lodges in larger quantities here and can be detected deep within the median portion of the groove. With a needle, the mass of grains which cluster together can be removed and separated with care. A small mass, only a fractional part of what still remained, showed, with a focus of one-fourth inch objective, hundreds of pollen grains. The long shaft of the bill also had upon its surface a few scattered ones. The most noteworthy phase of this subject remains yet to be recorded when the feathers are analyzed in greater detail, for here is to be found the real means of scattering the pollen, or pollination. The chief repositories having been just described as occurring below the angle of the mouth and in the median groove under the lower mandible, it remains to mention the part taken by the feathers. There are four ways by which the pollen becomes engaged or held by the feathers, which will be better understood after the anatomy of the latter structure is touched upon. The feathers from the sides of the head, lores, and below, are mainly instrumental in this work. In general, they are much like feathers of other birds, of the contour type, plumulaceous at the base, composed of a short, weak calamus, a rhachis, vanes, barbs, and barbules, the latter being peculiar in that at the extremity of the vane the barbules are armed with sharp, thistle-like projections (barbicells), some of which are somewhat curved. The vanes at the base of the feathers arc long and thread-like, near where they join the .shaft are flattened, oar- fashion, as seen in Fig. 4. Little pointed barbs divide these filamentous vanes at regular, short distances. One of the methods of carrying pollen is here met with, between two of the vanes, as shown. The vanes of the upper part of the main body of the feather are made up of narrow, acute plates or barbs, resting close together. The barbs of another vane encroach or touch the liarb of a neighboring vane, so that between them are found entrapped many pollen grains, as demonstrated in Fig. '2. Another way by which pollen is ADAPTATIONS IN ANIMALS AND PLANTS 47 effectually engaged is by being held between two of the barbs, which are merely spread apart, giving room for the grain, as in Fig. 3. The fourth method observed of carrying these fertilizing agents is an extraneous one, depending upon the glutinous secretion from the stigma of plants that adheres to the feathers, thus assisting the pollen to stick fast to the feather. Through a high magnifying power is seen the thistle-like ending of the vanes, the barbules frequently matted together by the sticky secretion referred to, gathered from the flowers while the birds are in search of food. Attached to the many pointed and flattened surfaces are seen pollen grains of many kinds, chiefly of very minute size, ready to depart or be taken on anew at the next visit to a flower. In flowers in which the wind is the agency for carrying the pollen, the grains are usually small, light, and more or less dry and spherical, while in insect flowers, the pollen of which is carried from one plant to another by insects in search of honey, the parts are variously adapted to cause the grains to adhere to the hairy underside of the insect's body to promote their dispersion. In bird pollina- tion the grains are carried in such diverse ways that this, together with other data, combine to make it possible that the humming-bird is the most wonderful distributer of pollen known to the animal world. I am not content to leave the subject without noticing that, as compared with insects, the local range of flight of humming- birds is undoubtedly greater, and during the regular migra- tions they make extensive flights, as I have already indicated. Their summer home in eastern North America extends from the Gulf of Mexico to half way across the British Provmces and from the Atlantic Coast to beyond the Mississippi River. In winter its range is southward, reaching into southern Florida, into Veragua and the eastern portion of the Isthmus of Panama, about eight degrees north of the equator. The equivalent of some 2,000 statute miles is thus represented in the migrations of this diminutive bird. The pollen taken en route during migration, as the humming-bird takes its sip of nectar from flower to flower, may gather in its repositories and be trans- ported from place to place anywhere throughout its range. 48 NATURE SKETCHES IN TEMPERATE AMERICA That some strange pollen grains are found entangled upon the bird is not surprising, especially in the spring. Taking all these suggestions into consideration, what wonder is it that we are called upon to say that the phenomenon of so wide- spread a means of pollination of plants by the humming-bird is perhaps unparalleled. In conclusion it may be said that some colors of flowers serve to make them visible and easily recognizable by insects, which are attracted thereto by the secretion of nectar and pollen. White flowers are nearly always excessively fragrant and are visited by night-flying insects. Bird flowers which have almost no fragrance, usually secrete an abundance of honey, are bright colored, and are visited in daytime by humming- birds. Both forms of these flowers seem to blossom at a time when their guests appear in greatest abundance. Male Ruhii-throatcd Humming-bird {Trochilius colubris). ADAPTATIONS IN ANIMALS AND PLANTS 49 Ihe Little Fear-Shaped House ON THE WiTCH-HaZEL BoUGH ^VERY one remembers the child- hood rambles among the hazel bushes, and the green clusters of nuts growing upon their branches. How many times have we tasted the acrid coverings and turned them back to determine their stage of ripeness! This reminder is probablj^ all that is neces- sary to dispel the possible confusion between the hazel shrubs and those of the witch-hazel, which are seemingly less familiar to the average person, but for the sake of those who do not recall the witch-hazel shrub, the illustration on this page will aid in this identification. The seed capsule of witch-hazel is quite unlike that of the hazel nut, the former being outwardly formed something like an acorn covered with pubescence. The basal portion of the seed receptacle is like a little saucer, with four projecting processes, and colored the same dingy green as the top. The apex is divided into two small lips which are turned a trifle outward and are spined at the middle. In the fall, some of the witch-hazel branches are often fairly covered with the seed capsules, and when ripe they snap apart in the middle with considerable violence, throwing the hard, woody seeds in every direction over the surrounding ground. Frequently, in the open forests where these bushes abound, they attain a height of from ten to twelve feet. On the branches of the witch-hazel one mav come across 50 NATURE SKETCHES IN TEMPERATE AMERICA some queer little prickly, pear-shaped galls, to which our attention is here directed. What an interesting piece of architecture one presents! It is covered with spiniforra pro- jections externally, while at the attached extremity it has a little round doorway. In the early summer, these spiny galls are greenish in color, but in the fall they shrivel and turn dark brown. One day, on dissecting some of these galls with the blade of a pocket knife, I found that they were shaped into a hollow shell, daintily lined inside with a fine frost-like coating. Under the magnifying glass I found a clue as to who the archi- tect was, though he had doubtless disappeared some time before. He had, however, left some cast-off skins and waxy secretions, and through this means I identified him as a species of plant louse, Ilaitiamelistes spinosus. The gall has a single roomy chamber and its entrance opens in a funnel-shaped doorway at the small attached extremity. Through this ojiening the tenants have free access to the outer air. On further search, I found among the whitish particles the remains of some Brachonid parasites. Here, too, a live .spider was found, hidden among the exuvise. Each one of these dwellers had its day of residence. But the spider was determined that no more strangers should enter, and had sealed the j)assageway against further newcomers with strands of silk. It was not until the following season that the opportunity finally came of my making the acquaintance of the adult, migrant, gall-making plant louse. On August fourth, when ex- amining one of these galls, there poured forth from the entrance a quantity of aphids in the pupa stage. They soon swarmed out from the entrance of the gall upon the stem of the witch- hazel twig, and in the course of several hours they had nearly all shed their last skins. As fast as these pupie shed their final epidermal coverings they flew away, dispersing in the air. Where they went will be described in the sequence. I took the opportunity of photographing the branch of witch- hazel containing some of the aphids as they were making their final departure from the gall, as shown in the illustration. From Pergande, we learn that the early generations live upon the witch-hazel. The eggs are laid between the crotches ADAPTATIONS IN ANIMALS AND PLANTS 51 The Spiny Gall on the Witch-hazel, showing the gall-producing aphid (Hamamelistes spinosus) in the act of leaving the gall to fly to the birch trees. The stem mother which produces the gall is showti in the upper right of the plate. 52 NATURE SKETCHES IN TEMPERATE AMERICA formed by the twigs and petioles of the flower buds. The young, after hatching from these eggs, settle down on the side toward the twig near the base. In one of the grooves of the buds, the young individual called the stem mother (see plate) inserts her beak, and feeding on the juices, together with some subtle, irritating substance which she injects, causes the remarkable transformation of the embryo bud into the spiny gall. The formation of the young gall is quite rapid, the bud on the side toward the insect lengthening and growing over the gall-maker. At first it is a rosy color, but after a time, when it becomes about half-grown, it loses the red tint and becomes green. By the end of June or the beginning of July it is mature. Within the chambered house, the stem mother has become very prolific, giving birth to as many as two hundred of her own progeny. Early in July, or about a month and a half after the hatching of this stem mother, the earliest migrants, her descendants, are fully developed. They then commence leaving the gall and continue to issue forth until late in the fall, migrating to the leaves of the birches where they dejK)sit their larvjv. The latter, after feeding on the birch leaves, settle down close to the bud, getting ready for their transformation and for hiiiernation. These larva' rej)resent the third, or Coccidiform, generation and their growth is very slow, many of them perishing here before spring, so that few adult females survive. These Coccidiform adults that come forth deposit their larvae on the tender leaflets just budding out. By their sucking process, irritation is set up at the edges of the young leaves, making certain changes that cause them to turn tlown and also cause bulging of the upper surface. This gives rise to corrugation, or pseudo-galls, of reddish or crimson color. It must be remem- bered that this is fpiite a different gall from the spiny gall on the witch-hazel, yet produced by the same insect species. Between the folds of the gall these insects live and grow rapidly, reaching full development by the end of April or early May. The fourth generation is quite unlike the Coccidiform generation. It is during the fifth generation that the winged return migrant is produced, which is nuich smaller than those leaving the witch-hazel, and it returns to the witch-hazel ADAPTATIONS IN ANIMALS AND PLANTS 53 in June. From these individuals are produced the sixth genera- tion. The sexes now come together for the first time and after union lay their eggs on the witch-hazel. These eggs in turn hatch into the stem mother first described. The sixth genera- tion are wingless forms and reach maturity in two or three weeks. Their eggs are laid about the middle or end of June and it is the young from these eggs that hatch about the time the flower buds are developing on the witch-hazel. In this cycle of life is exemplified a remarkable case of par- thenogenesis, or the giving forth by birth of individuals from an unimpregnated female. The virgin female here has the latent power to give birth to live larvae, and each generation, from the first to the sixth, has similar power. All the adult females have some easily recognizable differences in structure, and the whole cycle starts over again each alternating year, commencing with the egg. Cockerell has advanced the idea of accounting for the evolu- tion of galls on the theory that the secretions of certain earlier mining insects caused a swelling to appear, where the larvae lived, on which excrescence they fed. " It is easy to see that the greater the excrescence, and the greater the tendency of the larvae to feed upon it instead of destroying the vital tissues, the smaller is the amount of harm to the plant. Now the continued life and vitality of the plant is beneficial to the larvae, and the larger or more perfect the gall, the greater the amount of available food. Hence natural selection will have preserved and accumulated the gall-forming tendencies as not only bene- ficial to the larvae, but as a means whereby the larvae can feed with least harm to the plant. So far from being developed for the exclusive benefit of the larvae, it is easy to see that allowing a tendency to gall-formation, natural selection would have developed galls exclusively for the benefit of the plants so that they might suffer a minimum of harm from the unavoid- able attacks of insects." ^ The great number and variety of galls agree in presenting a more or less elaborate structure, says Romanes, ^ which is not only foreign to any of the uses of plant life, but singularly 1 Entomologist, March, 1890. 2 "Darwin and After Darwin," Part I, p. 293. 54 NATURE SKETCHES IN TEMPERATE AMERICA and specifically adapted to those of the insect life which they shelter. Yet they are produced by a growth of the plant itself when suitably stimulated by the insects' inoculation — or, ac- cording to recent observations, by emanations from the bodies of the larvse which develop from eggs deposited in the plant by the insect. Evolution may have acted through the insects, for "it may very well have been that natural selection would ever tend to preserve those individual insects, the quality of whose emanations tended to produce the form of galls best suited to nourish the insect progeny; and thus the character of these pathological growths may have become ever better adapted to the needs of the insects." The Guests of the Wild Bergamot In late summer the wild bergamot often grows in clumps covering large patches of ground, in pastures, fields, and road- sides. Where these flowers are thus assembled, bunil)lebees and butterflies are often seen drinking the sweets. It is not until one carefully studies the flowers of this j)lant, together with its insect guests, that some interesting facts are brought to light concerning adaptations. In the first place, the tubes of the flowers are seen to be c|uite long, indicating that they are more nearly adaj)ted for long-tongued insects such as butterflies and moths. Accortling to Robertson, the peculiar form of the tube, the two-lipped corolla, and the position of the stamens and style, indicate that the flower is a modification of a flower originally adapted to bumblebees. The level-topped heads, the erect corollas, the exj)osed organs, and rose color make it an attrac- tion for butterflies, — the principal guests. Pammel says that the Iowa flowers, as well as those of Wyoming and Colorado, are frequently visited by bumblebees, though butterflies are not uncommon on the flowers in Iowa. In Michigan, I have found that the bees far outnumber the butterflies as frequent- ers of the flowers. These flowers are probably in the process of active changes from bee flowers to butterfly flowers. The change is, perhaps, somewhat hindered, owing to the different insect visitors they ADAPTATIONS IN ANIMALS AND PLANTS 55 The Wild Bergamot (Monarda fistulosa) and its little yellow butterfly visitor, Terrias lisa. 56 NATURE SKETCHES IN TEMPERATE AMERICA have as guests from year to year. One species of butterfly which is frequently found on the blossoms is the pretty little yellow species, Terrias lisa, which is shown in the illus- tration, just as it is about to alight on a flower. As the larvse of this insect feed on a species of cassia and on clover, the visits of the butterfly to the wild bergamot are for nectar. It must be admitted that structures of flowers often appear to have indifl"erent characters which are difficult to account for on the ground of natural selection. It is, however, more often our ignorance of the complex life as well as a quantitative analysis of variations of a flower that lead us astray in inter- preting these structures. ,¥2^-c" The Seasonal Pko( kssiun of the Flowers, Insects, and liiuns ^^21 tions oi nati ARDLY can we realize the changes being \\ roiiulit in the woods and meadows unless we 'lose touch with the varied condi- ture. On August twenty-second, after a night of rain, I find the following summing up of the day's reflections: The flowers of the wild bergamot, which a few weeks ago appeared in their best colors, are now fast fading. It is rare that a per- i feet, fresh flower can be found unless it may be one growing in some shady spot. With the going out of the bergamot are contrasted the cardinal flowers, which are now A' ADAPTATIONS IX ANIMALS AND PLANTS 57 The Troiliis Butterfly {Papilio troilus) visiting the Cardinal Flower {Lobelia cardinalis). This butterfly, along with the ruby-throated humming-bird, aids in the cross-fertili- zation of this flower. It mimics the butterfly Pharmacophagus (Papilio) philenor on both upper and lower wing-surfaces. See colored frontispiece. 58 NATURE SKETCHES IN TEMPERATE AMERICA at their height. I found them at one point skirting the wet woods; in another they grew in the swampy portions of the meadows, giving a glorious effect to the plant groups there gathered. Here I saw the black butterfly, Papilio troi- lus, as shown in illustration on page 57, flitting down upon these blossoms, dividing its time, one moment here and the next moment on the boneset. I have just observed this exquisite swallow-tail as it flits away, to be suddenly replaced by the allied species, philenor. In its turn comes the dashing little ruby-throated humming-l)ird that especially loves to delve in these blossoms, while keeping company beside it is the bumblebee, Bombus amcricanorum, which sometimes illegiti- mately steals the nectar through tiie slit. On viewing these brilliant cardinal flowers, one is reminded of Robertson's remarks concerning them: "The pendent lip shows that the flower is intended to be visited by a bird or insect which is in the habit of sucking the sweets from flowers without resting upon them." ^ What a suggestion in the phil()S(){)hy of the flowering seasons lies here; the procession of the flowers being timed to the appearance of this bird as well as tlie l)ees. But I have already touched upon this topic more at length in the part on Bird Flowers. At this time the pods of the large, common milkweed are well develoi)ed, while the flowers are getting scarce. The white blossoms of the wild carrot are presenting their exquisite heads; they spring up in the mowed fields, breaking the monotony of the wide, open stretches. The bugle-weed, like the boneset, now thrives luxuriantly, .seemingly competing with the goldenrod in suitable places. Blight among the leaves of plants, parasitic invasion, and the many ragged leaves from the attacks of developing larvae or hungry grasshoppers, bring on a noticeable change; withering and senescence show their effect on the one hand, while on the other hand new life springs into existence. The flowers of the button bush have entirely disappeared; the green seed balls now hang from the bushes. With the dropping of the white flowers there passed a beautiful scene of insect activity about the.se perfumed heads. Peering out ^Botanical Gazette. Vol. XVI. 1891. ADAPTATIONS IN ANIMALS AND PLANTS 59 near the top of the giant mullein stems, which have taken on a brownish hue, are just a few of the yellow blossoms. As I wander through the wet meadow, I find in various stages of blossoming the daisy and common fleabane, the spotted jewel weed near the woods, scattered vervain, knotweed, evening primrose, self-heal, Joe-pye-weed, pearly everlasting, and pasture thistles, showing their season of blossoming. In my previous rambles I have noted the progressive steps of growth, maturity, and senescence through the seasons, the maximum number of flowers seeming to appear and to be timed to correspond to the presence of the greatest number of insects upon which the flowers are dependent for fertilization. At this time among the thickets of ferns, the matured katydids, the meadow grass- hoppers, and the crickets are answering each other from every quarter with their day calls; while there is an appreciable increase everywhere in mature grasshoppers and locusts. Among the open groves of trees new cicada songsters are heard, adding more and more to our procession of maturing life. Little by little the barn swallows are flocking together, getting in readiness for the pending vital migration. The clump of wild rose bushes in the pasture, which furnished so much interest, of late has lost its little nestling song sparrows. They have reached the proper age and dignified size to leave the nest and are being fed by the parents in the willows. The flight into the bushes shows the muscular power of their ^vnngs to be excellently developed, and the family of four are accumu- lating strength for the advent of migration, and thus we view the fast changing scenes. 60 NATURE SKETCHES IN TEMPERATE AMERICA ^'v What the Polyphemus Moth and Caterpillar Suggest HHE moth j^iven in llu> illustration above is a common species, known as Tclca poh/plicmus. Toward the end of July and durinfj August, I found the full {frown larvu> of this moth on the leaves of the oak and lime trees. It is said to feed also on the leaves of a great variety of trees, including birch, maple, elm, chestnut, sycamore, and beech. The caterj)illar of this moth, shown in the illustration, is a delicate shade of green, having the sides of the body orna- mented with lines of pure white. The feet and head are brown, while there is a V-shaped border of the same color at the end of the body. It is here figured in a state of rest, the body being contracted in length. The hairy warts are tinted with orange and red in life. It resembles the luna caterpillar quite closely, but its food habits are somewhat different as the latter is found almost entirely on the walnut and hickory. The cocoon of this caterpillar is made like that of the luna moth, being usually constructed of two or three leaves drawn together with silken threads. Within this recess of leaves it spins a very densely woven structure, and into the fibres composing it the larva mixes a brownish substance that soon dries and hardens. The cocoon is about an inch and three- quarters in length. After its completion, the caterpillar pro- ceeds with its transformation into the pupa stage. In the ADAPTATIONS IN ANIMALS AND PLANTS 61 The Pohjphemus Caterpillar on basswood in contracted attitude. This large larva is excellently protected by its green coloration against the leafy background in its natural surroundings. 62 NATURE SKETCHES IN TEMPERATE AMERICA fall their cocoons drop to the ground where they remain until late spring or early summer (June) when the moths finally emerge. The polyphemus caterpillar is often the victim of the ichneumon insect known as Ophicn macrurum; the latter parasite laying its eggs on the skin of the caterpillar's body and finally causing its death. Before reaching maturity this larva passes through five different larval stages, or four moults; Trouvelot^ states that he has observed six larval stages. Sometimes the eggs of the moth are parasitized by the little parasitic insect, Telenomns sphingis. In warm seasons when the summers are very long, there appear to be two broods. The large, ochre-colored moth, whose wings expand over five inches, is subject to great variation, as many as six varieties being recorded. The moth, at about the middle of the fore- wings, presents a transparent spot encircled with a very thin edging of black. The front margin of the wings is gray, while just behind it the ground color is often tinged with brown; near the ba.se of the forewings are broken white lines, edged outwardly with black or dark brown. There is a dark, curved, clouded line that extends across the lower wings parallel with the edge, and is continued on the anterior wings forward more than half-way acro.ss. The hind wings are exquisitely marked, bearing a conspicuous eye-like window near the middle, mar- gined with dee{) black and inwardly reflecting a blue shading, which disappears into the black. Darwin suggests that the eye spots on the hind wings of moths are pierced by birds in their attacks on these insects and thereby save the vital parts from destruction. The geograjjhical range of this species is across the entire continent of America, extending into Mexico. There are .several questions that present them.selves as we review the above sketch of its life history. These resolve themselves as follows: First, the cause of the seemingly great abundance of this species; .second, the cau.se of the number of varieties; third, the cau.se of its polyphagous habit, or ability to feed on a great variety of food plants; fourth, the cause of the wide distribution of the species. It is obvious that the abundance of this insect shows that ^American \aturalist, Vol. I, 1867. ADAPTATIONS IN ANIMALS AND PLANTS 63 it is well protected in some important ways against its enemies, notwithstanding the fact that many individuals are sacrificed in the egg and larval stages by parasites, and later on in life, by larger enemies. The tubercles and hairs of the larva, as well as the markings, play an important part in protecting the body against birds and lizards. Moreover, the green larvae are well protected when on their food plants, for I have repeatedly observed how perfectly they blend against the leafy background. There are undoubtedly other unknown factors, besides those considered, which act in a beneficial way to pre- serve the species. As to the variations noted in this species, I surmise that the color varieties may be influenced by the larvae feeding on diverse food plants, and the difl"erence in the amount of nourish- ment they obtain thereby. Then, too, there is the dift'erence in the temperature and humidity the species is subjected to, as a result of covering such a wide range of territory. Pictet ^ has shown in experiments on several moths, notably Ocneria dispar, that by changing the food of the caterpillars of one or two generations the moths showed great variations from the normal forms in color and size. The wide distribution of the polyphemus moth seems to have been brought about largely by the very fact of its adapta- tion to many food plants, polyphagous habits, which would facilitate its adaptation to new fields. It is obvious that a species living on many food plants would stand a much bet- ter chance of being preserved than if its food were restricted to one plant. Passing briefly in review, it is found that there is a series of adaptations which begin in the egg and end in the adult moth. Each stage has its special contentions independent of the others. It is easily conceived that out of the hundreds of eggs laid by this moth, comparatively few individuals, after escaping parasitism, pass through the struggle of life and are able to perpetuate the species. Yet in spite of the hazards encountered during the egg, larval, and pupa stages the polyphemus is one of our most common moths. Darwin - says in a letter to 1 Mentioned by Morgan, "Experimental Zoology." * "Life and Letters," p. 132. 64 NATURE SKETCHES IN TEMPERATE AMERICA Lyell, "I always repeat to myself that we hardly know why any one single species is rare or common in the best-known countries," Whether a species is abundant in a given locality is necessarily determined by natural causes. Chief among the conditions favoring existence of a species are its adjustment to its surroundings, that is, maintaining itself against competi- tion with members of the same species and other enemies, and the resistance to climatic conditions. I have attempted in the foregoing account to exemplify by the polyphemus moth some of its adaptations to these varied conditions. Protective resemblance in the .snout butterfly {IJbytlua back- vianni). The palpi project forward so as to resemble a stem, the underside of the 7vings simulate a dried leaf. This insect appears in May. III. PROTECTI^^ RESEMBLANCE, WITH EXAMPLES III. PROTECTIVE RESE]\IBLANCE, WITH EXAMPLES Darwin's Theory of Protective Resemblance WHEN we study animal life in general, it is remark- able how many animals are afforded concealment by their outer colors. This adaptation of external coloring to the conditions of life is often associ- ated with corresponding changes of structure and secures to the animal still further safety by concealment. In the one case it is color protection, in tlie other fc/rni protection, the two sometimes appearing in the same animal. Modification of color so that it assimilates with that of the surrounding environment has become highly sjjccialized in some animals. The protective hues of the small ground sparrows, the quail, grouse, and whip-poor-^\ill are famihar examples among birds, while in the whole family to which the grass- hoppers belong the insects present more or less monochrome color patterns that aid in their concealment. Wallace writes: "It seems to be in proportion to their slug- gish motions or absence of other means of defence, that insects possess the protective coloring. In the tropics there are thousands of species of insects which rest during the day, clinging to the bark of dead or fallen trees, and the greater portion of these are delicately mottled with gray and brown tints which, though symmetrically disposed and infinitely varied, yet blend so completely with the usual colors of the bark, that at a distance of two or three feet they are quite undistinguishable. " It will be remembered that Darwin ^ placed considerable stress on this subject. In his "Origin of Species" he says: "Insects often resemble for sake of protection various objects, 1 "Origin of Species," pp. 214, 215. 67 68 NATURE SKETCHES IN TEMPERATE AMERICA such as green or decayed leaves, dead twigs, bits of lichen, flowers, spines, excrement of birds, and living insects; . . . The resemblance is often wonderfully close and is not confined to color, but extends to form and even to the manner in which the insects hold themselves. The caterpillars which project motionless like dead twigs from the bushes on which they feed offer an excellent instance of a resemblance of this kind. The cases of the imitation of such objects as the excrement of birds are rare and exceptional. . . . But in all the foregoing cases the insects in their original state no doubt presented some rude and accidental resemblance to an object commonly found in the stations frequented by them. Xor is this at all improb- able, considering the almost infinite number of surrounding objects and the diversity in form and color of the hosts of insects which exist. As .some rude resemblance is necessary for the first start, we can understand how it is that the large and higher animals do not (with the cxcej)tion, as far as I know, of one fish) resemble for the sake of protection special objects, but only the surfaces which commonly surround them, and this chiefly in color. Assuming that an insect originally happened to reseml)le in some degree a dead twig, or a decayed leaf, and that it varied slightly in many ways, then all the variations which rendered the insect at all more like any such ()l)ject and thus favored its escaj)e would be preserved, while other variations would be neglected and ultimately lost; or if they rendered tlu' insect at all less like the imitated object they would be elimiuatod." Wallace placed both protective resemblance and mimicry in the same category, claiming l)oth to have resulted from natural selection. But there are a certain number of English naturalists, including Poulton, who have elaborated on this subject and have contributed a quantity of very interesting data in su])port of the desirability of drawing a distinction between protective resemblance and mimicry. The supposed difference between them is that in mimicry one animal mimics another living animal, in contradistinction to an animal that resembles the surrounding medium in which it lives. Of late, moreover, there has arisen another group of physiological ex- perimenters who place the coloration of animals on a chem- PROTECTIVE RESEMBLANCE. WITH EXAMPLES 69 ical footing, giving a physical, as distinguished from an aesthetic, explanation. Besides the examples given above, there are in the temper- ate region a number of common animals that clearly show protective resemblance. For instance, color resemblance is seen in the tree-toad, which resembles the gray or lichen- colored bark; the bark weevil, which simulates the uneven surface; the catocala moth, whose mottled wings blend with the bark. The foregoing are examples of a type of color that blends with and simulates the general background of their environment. There are others which bear form resemblance, illustrated by such examples as the walking-stick, which resembles a leafless twig, moths which resemble bird droppings, and those which can scarcely be distinguished from a dried leaf; others like some of the Plusia moths, which often alight on the ground, appearing like broken-off twigs. With the exception of the latter, all of these forms are described elsewhere in this book. Poulton has divided the colors of animals as follows:^ I. Apatetic Colors Colors resembling some part of the environment or the appearance of another species. A. Cryptic Colors. B. Pseudosematic Colors. Protective and aggressive False warning and signalling resemblances. colors. 1. Procryptic Colors. 1. Pseudoposematic Colors. Protective resemblances. Protective mimicry. 2. Anticr\-ptic Colors. 2. Pseudopisematic Colors. Aggressive resemblances. Aggressive mimicry and alluring coloration. II. Sematic Colors III. Epigamatic Colors Warning and signalling colors. Colors displayed in courtship. 1. Aposematic Colors. Warning colors. 2. Episematic Colors. Recognition markings. ^ This classification has been elaborated by Poulton in his work on " The Colors of Animals," and also in a more recent work by him. 70 NATURE SKETCHES IX TEMPERATE AMERICA Wallace sums up the various modes in which color is produced or modified in the animal kingdom as follows: "The various causes of color in the animal world are molecular and chemical change in the substance of their integuments, or the action on it of heat, Hght, or moisture. It is also produced bj' inter- ference of light in superimposed transparent lamellae, or by excessively fine surface striae. These elementary conditions for the production of color are found everywhere in the surface structure of animals, so tiiat its i)resence must be looked upon as normal, its absence as exceptional. Colors are fixed or modified in animals liy natural selection for various purposes; obscure or imitative colors for concealment; gaudy colors as a warning; and special markings, cither for easy recognition by strayed individuals, females or young, or to divert the attack from a vital part, as in the large, brilliantly marked wings of some butterflies and moths." Colors are jjroduced or iulonsified by processes of develop- ment, either where the iiiteguinent or its appendages undergo great extension or modification, or where there is a surplus of vital energy, as in male animals generally and more esjiecially at the breeding season. Colors are also more or less influenced by a variety of causes, such as the nature of the food, the phot()gra])liic or ])hysiological action of light, and also by some unknown local action, probably dei;endent on chemical peculiarities in the soil or vegetation. These various cau.ses have acted and reacted in a variety of ways, and have been modified by conditions dei)endent on age, or sex, on competi- tion with new forms, or on geographical or climate changes.^ According to Tower, the colors of insects, when grouped according to their causes, can be assigned to three categories: namely, chemical or pigmental, j)hysical or structural, and chemico-physiological or combination. The colors due to chem- ical or pigmental changes are black, brown, orange, yellow, drab, many reds, rarely blue, green, and white. The pigments which produce them are soluble in various reagents. These compounds nuiy be the product of the metabolism of the animal, or derived from food, or they may be accidental inclusions. »" Natural Selection and Tropical Nature," pp. 391, 392. Of other specific causes may be mentioned temperature and moisture. PROTECTIVE RESEMBLANCE, WITH EXAMPLES 71 Hagen divided color-producing substances into dermal and hypodermal, the former being located in the cuticula and the latter in the cells of the hypodermis which lies under the cuticula. Poulton has shown the existence of color pro- ducing substances in the fat body and hsemolymph, which Tower designated as subhypodermal colors. Wallace states that the pigmental colors have a different character in animals according to their position in the integument. These epidermal or cuticular colors appear in the external, chitinized skin of insects, in the hairs of mammals, and partially in the feathers of birds. To the hypodermal colors belong many of the reds and yellows of butterflies and birds. Tower relates that the dermal colors and the substances which produce them are located in the outer portion of the cuticula and are diffuse pigments, which is contrary to the views of Hagen and Enteman who maintained that they were present in the form of granules. The hypodermal colors are usually in the form of granules located in the hypodermal cells or more rarely derived pigments. Many of them fade after death, while others are permanent. Physical or structural colors are usually produced by tlie interference of light, either by reflection or by fine strite, or modification in some way by the light impinging on the body. These results are brought about by polished surfaces, lamellae, pits, striae, scales, or other modifications. White is the only physical color in insects, which is produced, according to Poulton, by the enclosure of minute air bubbles or transparent globules often enclosed in scales, which scatter the various rays in all directions. White is also produced by the flat faces of crystals and by fine granules in the fat body. The physical color, so-called, or white, is usually combined with chemical or pigmental colors, which give varied and brilliant hues to insect coloration. The chemico-physical cr combination colors are explained by the light of one wave length being neutralized, owing to one set of such waves being retarded or shifted so as to be half a wave-length behind the other set. The complementary color of that which is neutralized is seen. To this class belong glossy or metallic tints in insects and in birds, and also the iridescent blue, red, green, and violet hues. 72 NATURE SKETCHES IN TEMPERATE AMERICA These colors are often produced by pigment and striae in the same scales of butterflies. The laws which Wallace believed governed the production of all cases of protective resemblance were rapid multiplication, incessant, slight variation, and the survival of the fittest, in other words, natural selection. Those cases which furnish striking examples of protective resemblance, such as the walk- ing-stick and leaf-like insects, represent instances in which the process of modification has been going on during an immense series of generations. The great majority of such species occur in the tropics where the conditions of existence are most favoral)le, and where climatic changes have for long periods been hardly perceptible. The Tree To.\d ^ CARCELY a week passed during spring and summer that I did not come across the tree-toad in my walks afield. In April its song was heard at twihght, emanating from the lowlands at the border of ponds, ditches, and wet meadows, or from the shrubs and trees nearby. During sum- mer, one of its favorite places of retreat in the daytime was in the shade of the wooden rafters imder the roof of a neighbor's porch. Again, the little pockets on the trunks of beech trees in the woods were especially attractive places for them. In September, the openings into the old apple trees often afforded choice locations in which they took up PROTECTIVE RESEMBLANCE, WITH EXAMPLES 73 their residence, staying in the cavernous interior until frosts. The photograph shows a tree-toad on the bark of a water beech, taken in the middle of July. In this species the stripes on the legs are much less variable than those on other parts of the body. These show very plainly in the photograph. The color of this individual was almost white with grayish mottlings. Against the background of the bark it presented an excellent example of protective The Tree-toad {Hyla versicolor). He becomes invisible by changing his color within an hour to harmonize mtk the green leaves or gray lichen-covered bark. resemblance. This effect was even more striking before the little subject suddenly turned crosswise on the bark as I was about to open the camera shutter. It is only occasionally that one hears the sound of the tree-toad in July In the middle of the day I heard one while it was on the bark of a walnut tree. It uttered a shght clattering note, similar to the notes made by the red-headed woodpecker, and could scarcely be distinguished from it. One of these toads, which I had taken indoors, fed eagerly on grasshoppers and other insects, taken from my fingers. On 74 NATURE SKETCHES IN TEMPERATE AMERICA one occasion it caught sight of a full-grown female walking- stick insect which it seized about midway along its body. Then the toad doubled the insect up, bringing the two halves together, and slowly but surely began to swallow it. To facilitate the operation the toad used its front feet, much as we would our hands, guiding and pushing the morsel down its throat. In view of the great length of the walking-stick's body, it was surprising that such a small animal could swallow this insect whole without at least first removing the slender legs; but the tree-toad was fully equal to the occasion. The result of the meal was that the ungainly walking-stick {iroduced a noticeable angular protuberance at the side of the toad's body, which, however, was only temporary as it only lasted for an hour or thereabouts after it was swallowed. The appetite of the tree-toad for insects is prodigious, .espe- cially after its day's fasting. One evening I offered my toad guest one of the familiar saw-fly larva', wliich is a large, light colored, bulky grul) that feeds on the heart-shaped willow leaves. After the larva, which was at first curled up from fright, began to gain confidence and straightened out in its attempt to crawl, the toad became much interested in its actions. Then, after watching it intently a little longer the toad finally sprang toward it, catching hold of the forward extremity, and hastily swallowed a fourth of its body. The j)owerful larva now j)ro- tested by suddenly curling its body, at the same time becoming perfectly rigid. The toad was put at a great disadvantage by this manoeuvre and was obliged to disgorge the part swallowed, ))ut did not do so without a struggle to retain its hold. The larva then remained perfectly quiet, seeming to be conscious of danger, while the toad in the meantime made no further attempt to swallow it again, though standing over it and watching quite a while for a final move on the part of the larva. The performance of suddenly curling the body is quite characteristic of this and some other larvjr, and here I had convincing proof that this habit could be useful in the preserva- tion of the individual against the attacks of toads, and has quite a biological significance. How birds would act toward PROTECTIVE RESEMBLANCE, WITH EXAMPLES 75 this larva would be quite interesting to determine. The bold- ness and heroic courage of this httle tree-toad in attempting to swallow so large a larva was admirable. But what must be said of the courage of this same little batrachian which was displayed a few minutes later! I happened to have at hand a plump, half-grown larva of a large moth, Telea polyphemus. This green larva had been feeding on the leaves of hazel and was much larger than that of the saw-fly species. On seeing this larva the toad at once seized it and in a few moments had it half-way down, but after struggling some time with it the toad again disgorged its bulky prey. I later supplied the toad with its regular diet of beetles and small moths. Occasionally it ate cabbage butterflies and small dragon-flies which I caught in a net during the da^' and reserved for its supper. The tree-toad varies much in color, depending on the back- ground environment, humidity, and degree of light. On certain occasions it changes from yellowish white to a deep gray or brown, after moving to a new position in a darker place. Similarly, sometimes it may change from white to a beautiful green, or green and gray, if moved to a background of green leaves. This color transformation requires about an hour's time. The male and female are very similar in size and color, the former being distinguished principally by his darker throat and larger tympanum, or ear. This species can be distinguished from other tree-toads by the orange-yellow or brownish con- cealed coloring of the leg surfaces where they fold in contact. The eggs are laid in the spring of the year in small clusters in the water of ponds and marshes, and are attached to the stems of plants. They hatch into tadpoles within two or three days after they are laid. Dickerson states in her interesting "Frog- Book" that about seven weeks are required for the tadpoles to complete their metamorphosis. The little green frogs then leave the water for their land excursions. I believe from observation that the tree-toads, when common in a locality, exercise an important influence or control over insect life, especially in beech forests and swamps, and act as a selective factor. 76 NATURE SKETCHES IX TEMPERATE AMERICA The Habits of the Walking-Stick Among the most curious members of the Orthoptera, or grasshopper family, are the walking-sticks. This name is applied to these insects because of the resemblance their long cylindrical bodies bear to sticks or twigs of trees. I have found them in greatest abundance among the undergrowth and herbage in the mixed beech forests. Here, between the first of June and the last of August, the various green stages of the young insects are frequently met wnth, while after this period the large, mature gray and brown forms scatter out among the open woods. At this period, moreover, the adults are often found on the trunks of the fruit trees in orchards. The males are much smaller than the females, and not infrequently the former retain their green color in adult life. There is but one generation of these variable insects each year, the numerous eggs })eing dropped one at a time on the ground by the females in September. These eggs usually fall among the leaves in the forests. They are shining black and have a bright strijjc on one side whicli gives them a near resem- blance to a small .seed of some leguminous j)lant. Being laid in the fall, the eggs remain on the ground during the winter and hatch in the following spring. The first young apjjcar, as I have above intimated, about the first week in June, but the exact time of incubating and hatching varies to a considera- able extent. On June '^^i. 1000. I found the average size of the young to be tiiree-eigiiths of an inch in length. I never fully appreciated the value of the green color to young walking-sticks, and conversely, the use of the gray and brown colors to the adults, until one day on examining the foliage of a sapling oak I happened to lie in a position to look down upon a cluster of its rich green leaves. Here I observed a young, half-grown walking-stick astride one of the leaves. His body was directly in line with the middle of the leaf, with his head directed toward the stem. When I first discovered him his forelegs were, as usual, closed together alongside the slender antennae which projected forward. The leaves of this oak were deep green, with the light pale green veins contrasting somewhat conspicuously. The position of the insect was such PROTECTIVE RESEMBLANCE, WITH EXAMPLES 77 The Male Walking-stick (Diapheromera femorata). The charac- teristic attitude of protection is shoivn by the extension of the forelegs in front, one on each side of the slender antennoB. 78 NATURE SKETCHES IN TEMPERATE AMERICA that he stood over the veins, the legs being arranged almost parallel with them. From this view of his body, he was so closely in accord with the veins that he was almost invisible. I wondered at the time if this position was a mere coincidence or was a common behavior. It is obvious that in this attitude and at a little distance the young walking-stick may stand on the upper surface of the leaves and defy the sharp-eyed birds or other vertebrates to discover his attenuate form. While I found this resemblance of the walking-stick to the central and radiating veins of the oak and other leaves to be remarkably perfect, there is another point that I noticed in this connection worthy of consideration. I found that when these Orthoptera become unduly alarmed their usual impulse seems to be to seek the under surface of the leaf. After some study I also found that he is here even more protected than when standing on the upper surface, not only on account of the shadows cast on his body, but from the fact that the assimilation is nuide far more perfect by rea.son of the median and lateral veins of the leaves being more strongly and roundly in relief here than they are shown al)()ve. I have photographed one of these insects on the underside of the oak leaf just as I found it, that the reader may get a better idea of the remarkable pro- tection afforded by this resemblance to tiie veins. The resem- blance of the walking-stick to the venation of the oak can he demonstrated in cpiite a striking manner, if the main median vein with two pairs of laterals are cut out carefully with a pair of scis.sors. The result is a fair facsimile of the young walking-stick. Of course, in the position which the young walking-stick naturally assumes in foraging, it does not always accurately lie over the veins of the leaf, for the veins slightly alternate. I have foimd, however, by observations, that if the insect stands at any angle on the leaf, and if he is viewed from below, his resemblance to the veins is sufficient to protect him. The nearer the position of the body corresponds to the central vein structure the greater the safety from attacks. The oak is doubtless the most often chosen as the natural habitat of the common walking-stick, but I have often found the young at home on a variety of herbage, shrubs, and small trees, where PROTECTR^ RESEMBLANCE, WITH EXAMPLES Leaves of Red Oak. The upper figure shows a young Walk- ing-stick protected by its resemblance to veins of the leaf; lower figure a young Round-wing Katydid which is green in life, like the walking-stick, and almost invisible against the leaf background. 80 NATURE SKETCHES IN TEMPERATE AMERICA they live on the leaves. This in no way mitigates the special adaptation of his bodj' referred to, for I have found that his attenuated form resembles almost as well the leaf veins of various other plants. In the latter part of July, I found on the wild gooseberry two very small individuals. These young readily sought the underside of the leaves when they were rustled. In the accom- panying plate photographic illustration of the wild gooseberry branch, I have portrayed them on the upper surface of the leaves, though on the underside there were far more individuals. Again, in the plate photographic illustration of the oak leaves, the reader may also note a shadowy j)icture of another Orthopteran frequenter on the largest leaf near the middle. This is a young round-wing katydid, quite plainly visible to the eyes while viewed in nature, but in the j)hot()graph his dark, rich green body blends and appears like a shadowy out- line. This youthful individual walked stealthily over the leaf, protected by his dark green coloring which was effectually tinged with light brown. His blackish antennie were very long and l)roken by alternating dark and light rings. These ring markings were effective against the green of the leaf and faded parts which surrounded him. Even the camera with its sensitive film failed to bring out his distinctive features. The adult walking-sticks often exhibit a most singular per- formance when they are attacked or frightened. Either they walk off with an ungainly stride in their attempt to escape, or they may fall to the ground. In the latter case they often "play possum" by lying perfectly rigid on the ground among the debris, feigning death perfectly. On such occasions they will sometimes allow themselves to be handled and still retain the stiffened attitude for minutes, or even hours afterwards, without regaining their feet. One of these feigning insects which I brought indoors was left on a table at ten o'clock in the fore- noon and it stayed in the same position on its back until half- past three in the afternoon of the .same day, or a period of six and a half hours. In the meantime it passed faecal matter three times, showing that internal functions were actively carried on during this apparently intense nervous suspense. Preyer ascribed the "shannning dead" of insects to the PROTECTIVE RESEMBLANCE, WITH EXAMPLES 81 Wild Gooseberry Branch, sho2i'ing young green Walking-sticks (Diapheromera femorata) on the upper surface of the leaves. The upper figure is that of a saiv-fly. 82 NATURE SKETCHES IN TEMPERATE AMERICA influence of kataplexy or hypnotism, this state being induced by fright. Darwin looked upon the instinct of "shamming dead" as simply the result of remaining motionless and thus inconspicuous in the presence of its enemies; this instinct having developed by natural selection without ever having been of an intelligent nature. Those individuals which were least inclined to run away from enemies being preserved rather than those which rendered themselves conspicuous by move- ment. Romanes ' says, "There seems to be at least not more difiiculty in developing an instinct to remain motionless under certain circumstances, than in developing one to run away, and as a matter of fact, all animals which are protectively colored have either as cause or sequence developed their instincts in the former direction." In the above word sketch,! have stated that the eggs of these insects bear a clo.se resemblance to the seed of plants, and secondly, that the young show remarkable adaptation to a life on the leaves, their attenuate bodies being deceptively like the venation of the leaves. Finally, I will now call attention to the fact that the adults are protected in their resemblance to twigs even to the minutest detail. In the fall the sexes are found together in large numbers, in pairs, often on the bark of the forest and fruit trees. Again, I have found them on such shrubs as the sumach; here they are all but invisible as they hold on the main stems. When I discover them .sometimes by accident, I often marvel that they are ever seen at all by human eyes, so close do their bodies imitate the twigs. Even the leaf scars are wonderfully represented. And why, may I ask, do these in.sects choose as a place of refuge the very spot on the sumach where there are dead branches near the main stem? Here is certainly a group of insects for the naturalist to work on. The problems presented are certainly accessible })y experi- mental research, and if they are coupled with observations in tlie great biological experiment grounds of nature, there is still room for interesting discoveries. Such adaptations as are shown in the form and color of the walking-sticks are the most striking of any in our temperate fauna. They doubtless ofTer the most powerful argument in favor of natural selection. ' "Mental Evolution in .\nimals." PROTECTIVE RESEMBLANCE, WITH EXAMPLES 83 An Illusive Butterfly, AND ITS Flower Protector |N one of my excursions to the sand dune region of Indiana, in April, I occasionally saw a small white butterfly flit about in the air. When it descended near the ground it sud- denly disappeared so completely that I was at first at a loss to explain the cause. I afterwards discovered that the deception practised had been caused by the butterfly alighting on the little white flowers of Arahis lyraia. The resemblance of this butterfly to these flowers is so remarkable that e\'en a trained eye would easily overlook this insect in nature. When I came near, the insect was found with its wings folded together, and it was resting upon the small, pure white flower heads. In this position the protection was heightened by the disposition of the yellowish green markings on the underside of the lower wings. I seized upon the opportunity thus afi"orded to make a drawing of the insect shown in the colored plate. The green markings of the imderside of the wings are so arranged as to divide the ground color into patches of white, which blend with or simulate perfectly the petals of the clustered flowers. The eyes of the butterfly are delicate, pale green, and the antennae are whitish, all of which adds to the effective- ness of the blend. The flowers of Arabis have white petals, with the centre yellowish green as is also the calyx. There is a shade of pink outside the base of the petals. All in all, the adaptation of insect to flower here displayed is one of rare exquisiteness. One day, in May, I studied the behavior of three of these little butterflies, which are known by scientists as Anthocharis 84 NATURE SKETCHES IN TEMPERATE AMERICA genutia. They were quite active in the warm sunHght, and when I first saw them, two of them flitted about, here and there, one moment alighting on the flower of Arabis, and the next moment depositing their eggs on the stems. Again they would indulge in a sunlight bath on the ground, where they would alight and spread their wings as if enjoying the heat of the sun. At one time I came across a group of Arabis plants covering a small area on a wooded sand dune. On searching the flowers, one of these butterflies was found, resting on the flowers in the protected attitude above described. The wind was strongly blowing at the time, and the insect clung on the flower with more than ordinary persistence, turning its body so that its head was directed toward the source of the air currents. It was so persistent in its desire to remain on the flower, that it submitted to be taken up with the plant, and laid in a box. But after a time, on jarring the box accidentally, the insect became startled, and flew away. As long ago as 18(58, Wood ' pointed out that the little orange- tip butterfly, in England, often rests in the evening on the green and white flower-heads of an imil)ellifer()us plant, — the wild chervil, Anthcscns sylrestris, — and that when observed in this position, the beautiful green and white mottling of the under surface coniplctoly assimilates with the flower-head and renders the insect very ditticult to be seen. It is probable that the rich dark coloring of the underside of our peacock, tortoise shell, and red Adnural IjiittcrHies, answer a similar purj^ose. All of these })utterflies .seem to have a tendency to remain very still when on the flowers, giving one the erroneous impres- sion that they are conscious of the i)r()toction afforded by their surroundings. Grossbeck - mentions that he found this butterfly depositing its eggs singly on the stems of Arabis, usually below the terminal bud. On very large plants as many as four eggs are sometimes found. I have confirmed the.se observations. Hornig^ found this species of butterfly laying its eggs on the common plant known as mouse-ear, Sisj/mhriutn ihalianum. I found upon looking into the subject that wherever ' Wallace, in "Natural Selection and Tropical Nature," p. 43. * Entomological Sewn, May, 1908. ' Ibui., Vol. XVI, p. 252.' The Orange-tipped Butterfly \A)itlwcli(tris gemitia) Resting on floxcers qf Arabis lyrata. An exquisite case of pror tecfive resemblance. The figure at the right shores the markings on the upper surfiace qf the rcings PROTECTIVE RESEMBLANCE, WITH EXAMPLES 85 the food plant of this butterfly appears, it is reasonably certain both plant and insect will be found associated. For instance, the range of Arabis lyrafa, according to Britten and Brown, is found to extend from Ontario to Virginia and Kentucky, west to Manitoba and ISIissouri. It ascends to twenty-five thousand feet in Virginia, and occurs on rocky and sandy places. Now let us examine the range of the orange- tip butterfly under consideration, and we find in Holland's "Butterfly Book" that it ranges from New England to Texas, but it is not found, so far as is known, in the regions of the Rocky Mountains and on the Pacific Coast. Where this Httle butterfly occurs, it is likely to be quite local. I have only found it in the sand dune region skirting the border of Lake Michigan, which is particularly rich in objects of zoological interest. I have been told by John B. Smith that this but- terfly was very local in its distribution in New Jersey. It is single brooded in the northern states and I found it mating at Dune Park, Indiana, in May. In North Carolina, Holland found that it was double brooded, judging this to be the case because he found it late in autumn. There are numerous species of the orange-tips of the genus Anthocharis (Euchloe of some authors) in North America. They are all small white butterflies, having the apical region of the primaries spotted or banded with yellowish orange or crimson. On the underside of the wings they are usually more or less protectively mottled, as in the species genutia that I have described above, each possessing yellowish green spots or striae. The orange coloring of the apex of the fore- wings is confined to the male in some species, and this patch of coloring must be considered as of entirely different significance, biologically, from that on the underside of the ^"ings. The orange coloring is, perhaps, a distinguishing sexual mark belong- ing to the epigamic colors classified by Poulton. Darwin ^ cited the case of the orange-tipped butterflies in support of his theory of sexual selection. He says: "The same reason which compels us to believe that the lower surfaces have been colored for the sake of protection leads us to deny that the wings have been tipped with bright orange for the *" Descent of Man," p. 313. 86 NATURE SKETCHES L\ TEMPERATE AMERICA same purpose, especially when this character is confined to the males." Wallace.' on the other hand, maintained that the orange coloring may have served in directing the attack of birds away from the vital parts of the body and, therefore, were also pro- tective in character. I might add that the Httle butterfly, Anthocharis genutia, while polyphagous, that is, having the abihty to feed on various I)lants. lives on cruciferous plants, such as Arabis, Sisymbrium, and Cardamine. There is, however, a sulistance having a mustard taste, common to all these plants, which the larvje of these butterflies seem to enjoy. The butterfly probably func- tions as a cross fertilizer, as well as using them as food plants. This has contributed in establishing a reciprocal relation between them and their exquisite little butterfly guests. The Animated Rolled Leaf . X other chapters the subject of protective reseml)lance has been treated and demon- strated by the walking-stick, the geometrid larva, the automeris moth, and other exam- ples. This subject would not be given full justice without mentioning the rolled-leaf moths, belonging to the genus Datana. After a slight shower one morning in July, I made a search at the edge of a mixed beech forest where the trees are .somewhat scattered. I had strolk'd but a short distance among the undergrowth in quest of study material before I found three examples of the night-flying moths known as Datana contrada. It will be seen from the first plate illustration, bearing two figures of these in- sects, that they resemble a withered, rolled leaf. Recording these insects just as they were found in nature, the first example appeared on the green leaf of a brier, the second one on the wild raspberrj', and the third on the green leaf of the sassafras. These situations indicate that the moths showed '"Natural Selection and Tropical Nature," p. 371. PROTECTHT RESEMBL\XCE WITB. EXAMPLES ST Tico Moths (Datana conirada). Upper figure, pale indirid- ual, riewed from above, shotnng resemblance to a urithered roiled leaf: lotrer figure, a darker individual, riewed from the side, shovring arrangement of markings in simidation of reins and shadow in front. Plant leaves of irild raspberry. 88 NATURE SKETCHES IN TEMPERATE AMERICA an indifference as to the kind of leaf they chose to rest upon. Others found later were either on the ground or were near it, ranging within a distance of from two to ten inches above it. Those resting on the leaves showed, moreover, an in- stinctive indisposition to fiy when I carefully handled or picked the leaves. Three days previously, during a strong wind, my attention was drawn to one of these moths conspicuously exposed on the upper surface of a leaf, which remained there for a number of hours despite the waving of the plant by the wind. The marked indisposition of these moths to fly when I came near them indi- cates in an excellent manner an inherent behavior which seems to develop coincidently with adaptive changes of form and color to their surroundings. Another sjjccies of these rolled-leaf moths which I found possessing similar habits and associated in the same environ- ment with the foregoing species, is the Datana 07igussi. It is shown in the second plate illustration, also photographed from life. This is a strikingly beautiful insect and is richly marked. But little conception of its .specially protected life among forest herbage can be gleaned by viewing the usual museum specimens with their wings dried in an open position. In the daytime when these moths are resting and require greatest protection, the wings are clo.se to the sides, and it is in this position only that they ])re.sent the leaf-like form. The front of the thorax is colored a rich velvet chestnut-brown, the upper wings being transversely streaked with brown on a yellowish color ground, and the edges of the wings have a brownish, lightly .scalloped border. These colors and markings are highly variable, and thereby aid in matching the vari- ously colored dried leaves. Likewise, the oblique stripes bear a marked illusion to the veins. This moth, on the whole, presents a general, rather than a special resemblance to leaves. The dried leaves composing the background were mostly beech and averaged in length longer than the moth's body. They were thrown about on the groimd by the wind, causing a cri.s.s-crossing and over- lapping in arrangement. Again, some of them that were curled up quite strongly lengthwise, were of variable hues. PROTECTIVE RESEMBLANCE, WITH EXAMPLES 89 A Moth {Datana angiissi) vieurd from above, shoicing mark- ings in simulation of a dried rolled leaf. 90 NATURE SKETCHES IN TEMPERATE AMERICA Notwithstanding this, the color of these leaves as compared with the colors and form of the moth's wings, matched verj- closely, and, generally speaking, formed a most deceptive simulation. The oblique lines across the wings ran in the same direction as those of the rolled leaves on the ground and were highly suggestive of veins. When the moths are on the ground, perhaps the protective coloring and form of the moth are most deceptive. Yet it was remarkable how easily the moth, while it was on a green leaf, was taken for a dried leaf which had simply been arrested in its fall to the ground. Perhaps one of the most notable features of protection afforded these moths is tlie disposition of the chestnut coloring on the forward j)art of the thorax. This arrangement of color has the effect of an abrupt .shadow at the front end of the body, corresponding to the hollow and shadow at the stem end of the leaf. The distal ends of the wings often have a scalloped margin, simulating the opposite wavy or toothed margin of the leaf. It is obvious that this arrangement of the color and form of these insects is e.s|)ecially u.seful against the beech forest bed. The instability of form and color exhibited in these Datana moths is prol)ably due to the varying effect of temperature, light, and moisture, coup'led with a changeable environment, aiul the crossing of the color forms. Where intricate a(la])tations aj)pear in the adult, such as I have just illustrated, it not infrecpiently hapi)ens that the early stages, or instars, in their life history are afforded similar mechanisms of protection. I was much surprised one day later in August to find a leafless stem of a bush along the wayside adorned at the top by what looked like, at first glance, .some floral di.splay. My error was .soon discovered when the liranch was pulled down for closer inspection. This p.seudo-floral form was shown to consist of numerous Datana caterpillars grouped together in a bunch, in such a way as to ])roduce the illusion of a flower. Each little yellow striped caterpillar had .selected its place, acting its part instinctively. Both ends of the body of each larva were curved outwards, and all seemed as rigid and motionless as the petals of a flower. (See plate photographic illustration.) These little gregarious caterpillars still immature, were PROTECTIVE RESEMBLANCE, WITH EXAMPLES 91 Datana Caterpillars grouped at the top of a branch in simulation of a flower. They are striped and marked irith bright learning colors, and they disgorge a yellowish fluid when threatened. 92 NATURE SKETCHES L\ TEMPERATE AMERICA five-eighths of an inch in length. They were warningly colored yellow and striped with reddish brown. The head and legs, together with the last joint, which has two hairy appendages, were intense black. Their bodies were sparingly covered with quite long whitish hairs. When touched, these caterpillars disgorged a yellowish fluid from their mouths, which might make them distasteful to birds. While I have shown the protection afforded the imago and larva, the eggs of Datana do not share this immunity. They are open to the attacks of parasitic Hymenoptera. The species known as D. interrigima and D. ministra, we are informed by Girault ' are destroyed in the egg by the parasites, Telenomus and Eupelmus, respectively. The egg seems to be a vulnerable point of attack which nature has not perfectly protected. It may be, however, that these para.sitic Hymenoptera by increas- ing in numbers in one season may limit their own larval food supply. In the next .season this would cause a reactive extermination of their own species out of mere lack of the Datana larvje food supply, thus creating a condition of i.solation. Considering all these facts of the life history of Datana, what a remarkable display of illusive and protective devices seems necessary for its existence ! Romanes ^ says, when there is supplied to us the suggestion of natural selection as a cause presumably adccpiate to account for this continuous growth in the number, the intricacy, and the perfection of such mechan- isms, that it is only the most unpliil«»s()i)hical min