Ways of the Six-Footed
by Anna Comstock, 1903
Incomplete; there is a full text of this book about insects at Archive.org.
II
A LITTLE NOMAD
One warm August morning I followed a certain restful, woodsy path which soon led me to a partially wooded hillside. I found a shady resting-place under a pair of twin maple trees, where I settled contentedly in the grass with some downy young sumacs for neighbors. The blue waters of the lake twinkled up at me through the tree-boles, and a blue sky beamed down on me through the tree-tops. The breeze, playing softly with the leaves above me, and the soft swish of the water on the rocks below united in a soothing song, to which a cicada from his high perch was doing his best to perform a worthy obligato. I was tired of a world of work and care; and as I turned my footsteps toward this cosy nook I said to myself, "I will go where I can be alone." Vain decision and absurd desire! I had just arranged for myself a tree-trunk chair-back and was enjoying the nice bark upholstery when a grandfather graybeard came teetering along on his stilts, lettering his body down at rhythmic intervals to feel of my hand with his palpi to discover if perchance I were good to eat. Then a red squirrel darted up a young ash tree in front of me, the dark stripe on his side where the red and white meet being particularly vivid and dashing; at first he sneezed and coughed his displeasure at my intrusion and then sprang his rattle so suddenly that I wondered if it might be that squirrels have secreted in them storage batteries that may be switched at will from action to sound. Then a great butterfly, a tiger swallowtail, came careening down through a hole in my leaf canopy and alighted on a sunlit bush near me; there, in utter luxuriousness, he slowly opened and shut his wings in obvious enjoyment of his sun-bath. While watching him I noted that the maple sapling, on which he was resting, was in a bad way; its leaves were riddled with holes, varying in size from that of a bird shot to that of a small bean.
Now while I was tired of a world that lectured and talked and argued and did many other noisy things that wore on one's nerves, I was by no means tired of the great silent world that did things and made no fuss about doing them. So, when my butterfly drifted away, I lazily began to investigate the cause of the dilapidation of the maple leaves. There I found, as I suspected at first glance, a little nomad named the Maple-leaf Cutter, which pitches its tent on leafy plains and whose acquaintance I had made several years ago when I was employed to make its family portraits.
I plucked a leaf that had several oval holes in it and also several oval rings marked by a tracing of bare veins and translucent leaf tissue (Fig. 16); then I noticed an oval bit of leaf wrong side up on the upper surface of the leaf. A glance at this through my lens showed that it was made fast to its place by several bundles of glistening white silk. With a knife point I tore asunder these ropes and lifted the wee tent and found fastened to its under surface another bit of the leaf identical in shape but somewhat smaller. Suddenly from an opening between the two an inquiring head was thrust out with an air that said plainly, "Who's there?" I tore the two pieces of leaf apart to get a better view of the little inmate. He was a stocky, brownish caterpillar, about one-sixth of an inch long, with shields on his thoracic segments that shone like polished bronze and an anal shield that was dull purple (Fig. 17). His several simple eyes were in two such compact groups that they gave the impression of two keen, beady, black eyes, and I had a feeling that he was inspecting me through the lens. He was very unhappy and squirmy when removed from his cover, and he backed so vigorously that he backed half his length out of the rear end of his tent before he felt safe, and then remained very still. His loosened tent was lying bottom side up on the leaf; and owing to my clumsy proportions I was obliged to leave the labor of righting it to him; he gave it his immediate attention and went at it in a most workmanlike manner. He crawled halfway out upon the leaf and by a dexterous lift of the rear end of his body he brought the tent right side up and at one began pegging it down. To do this he moved his lower lip around and around on the leaf surface to make fast, then spun his rope up and lifting his head fastened it to the edge of the tent; this process he repeated many times, but with great rapidity, and when the fastening was finished it was well worth seeing. He has spun his silken cords so they formed an X. This arrangement allowed him room to fasten many lines to the leaf and tent, and since they were crossed in the middle they had the strength of many twisted strands (Fig. 18). He put his first fastening at one side of his tent and then hastened to put another on the opposite side, and thus made secure he took his time for putting down the remainder of his ropes.
While watching him spin, I mused on his history as revealed in its earlier chapters by that truly great scientist, Dr. Fitch, and added to in its later chapters by our own Dr. Lintner, --two men of whom New York is so justly proud. This history was as follows: Last May a tiny moth (incurvaria acerifoliella) sought out this maple sapling; she was a beautiful little creature with a wing expanse of a little more than a half inch; her front wings and thorax were steel-blue, and her hind wings and abdomen were pale, smoky brown; these hind wings were bordered with a wide, fine fringe; across both sets of wings glinted and gleamed a purple iridescence like that on the surface of a bit of mother-of-pearl. On her head, between her antennae, she wore a little cap of orange feathers, this color combination of orange and steel-blue proving her to be a moth of fine discrimination in the matter of dress. This pretty mother moth laid an egg upon the leaf which I held in my hand; from that egg hatched my wee caterpillar, and began life, I suspect, as a true leaf-miner. However, this is a guess of my own, inspired by the appearance of the leaf. Anyway, he did not remain a miner long, but soon cut out a bit of the leaf and pulled it over him and pegged it down; beneath it he pastured on the green leaf-tissues in safety, and in this retreat he shed his skin. With added growth came the need for more commodious quarters; so he cut another oval piece from the leaf, as much larger than his tent as he could reach with coming entirely out of his cover; before he it cut complete free he ingeniously fastened one side of it to the leaf with silk so that he would not fall, cradle and all, to the ground. He then used this fastening as a hinge as he came part way out of his tent, took a good hold of the leaf with his sharp claws, and flipped the loosened piece over his back and fastened it down over fresh feeding-ground. What was previously his tent was then a rug beneath him; his new pasture was a margin of about one-twelfth inch that lay between the edges of his rug and his tent; for he was ever averse to exposing his precious person to lurking enemies more than was strictly necessary. Before he shed his skin again he may have needed a new pasture; if so, he struck his tent and walked off with it on his back, looking like a Lilliputian mud-turtle, and finally fastened it on a new site (Fig. 19). He had already several times gone through this process of upsetting his house, for he had two rugs beneath him and two tents above him in graduated sizes. And I knew that some time in the near future he would peg down his largest tent more securely than he had ever one before, and there in this safe shelter would changed to a pupa. When the leaf that had been the range of this small nomad fell in the autumn he would go with it; and wrapped in his tent rugs he would sleep his winter sleep under the snow until he should awaken next spring, no longer a tenter on leafy plains, but a true child of the air.
I tore off a bit of the leaf on which my little friend had settled, and went over and pinned it to a leaf still on the bush. It may have been an absurd thing to do, but by this time I was shamelessly, nay, intrepidly sentimental, and I did not wish that little chap to starve because of my inborn tendency to meddle with other people's affairs. I then fell from bad to worse and began to moralize; for when a naturalist falls to moralizing science weeps. I meditated thus, "I came here to get away from puzzling problems, and yet here they are all around me; the problems of the little nomad; the problems of the poor, leaf-lacerated maple; and if I look in other directions I will find more in plenty." But for some sweet reason I did not feel about problems as I did when I ran away and hid from the noisy world two hours before. I was filled with a new sense of the dignity and grandeur of this great silent struggle for adjustment and supremacy which was going on around me. I felt inspired to go back and serenely do my own little part as well as I could, trusting that somehow, somewhere, and to Some One the net proceeds of struggle are greater than the cost.
III
A SHEEP IN WOLF'S CLOTHING
To hatch from the egg, to attain growth through steady attention to eating, to reach maturity and produce eggs for another generation, are the necessities of insect life. The ways and means of accomplishing these things successfully is a problem which is partially solved by the habit of the species, and partially by the efforts of the individual. The habits of a species comprise the wisdom stored up in the experience of that species during thousands of years; the habits of a specifies is the pathway which it has struggled up to the ranks of the "fittest" which have survived.
No insect history better epitomizes the history of a race than does that of the Viceroy Butterfly (Basilarchia archippus), a beautiful insect which in early summer makes our open fields and marshy meadows brilliant with the flashing of orange-red wings in the sunshine. The early stages of the Viceroy have been worked out in detail and given to the world through the careful and patient labors of Dr. S. H. Scudder.
The Viceroy mother select usually the terminal twigs of some willow or poplar, and places her eggs singly on the tips of the terminal leaves (Fig. 20). Now this choice of the topmost leaf of the branch is not without reason on the part of the mother. This egg, though scarcely so large as a pinhead has many enemies; there are spiders always prowling around to find tidbits for their rapacious stomachs; there are tiny ichneumon-flies ready to lay their eggs within so small an egg as this; there are wasps and other voracious insects always on the lookout for things eatable. So there is reason for putting these ones in a place on the tip end of a branch, where the wind always keeps the leaves stirring in a way to confuse the vision of these actives foes. As a protection against these same inquisitive eyes the egg is of a dark green color, almost the exact hue of the upper surface of the leaf on which it is invariably placed. This little green egg is a beautiful object when viewed through a microscope; it is ornately sculptured in an hexagonal pattern and set with short spines. It seems to be one of nature's laws of beauty that nothing is too small to be worth while.
After from four to eight days have elapsed since the egg was laid, a little brownish larva gnaws its way out through the side. As soon as it is fairly out it turns around and eats the egg-shell, carving, spines, and all. Not for sentiment nor yet for digestion does the larva perform this somewhat auto-cannibalistic feat; but for the very practical reason that the empty shell if left would mayhap yield a clew to his enemies which they might follow up to his undoing. Then the little caterpillar begins feeding across the end of his native leaf, leaving the midrib untouched. Maybe the midrib is too tough for the jaws of a baby caterpillar. On the other hand, his subsequent actions would seem to imply method in his manner of attacking the leaf; for the Viceroy larva is a night feeder, and he uses the denuded midrib as a perch during the day. Stretched out lengthwise on this he is nearly invisible during his earlier stages. Besides this, he uses a very ingenious device to distract the attention of keen eyes from his precious person; he fastens a silken thread a little bunch of debris to the bare stem between his feeding-place and his resting-place (Fig. 21). This is a clever performance; for if one of his foes should be hunting on this leaf and should start out on the denuded stem it would meet with this empty and worthless mass and would naturally be discouraged from further investigation. As the caterpillar gnaws off more of the leaf he moves his ambush bundle farther down the stem; so it is evidently of some real use to him.
After a few days our caterpillar finds his skin too small for his increasing size and proceeds to shed it caterpillar-wise; but he is still unwilling to leave any traces of himself around, so he eats up his old skin as he did his egg-shell. He soon destroys the leaf of his birth and then consumes others. In the course of his growth he sheds his skin three times and after each moult he assumes a change of form and color. Various warts and tubercles appear on him after the first moult; these grow more numerous and noticeable with each succeeding change until he becomes a most grotesque and amazing-appearing creature, with a pair of spiny pompons in front and spines too numerous to mention decorating his body. Most people not entomologically educated would exclaim on seeing this caterpillar when full grown "The horrid thing!" And if the caterpillar could hear and be conscious of the history of his race as embodied in himself, he would rejoice and be exceeding glad over this verdict; for it is greatly to his advantage now to look so disagreeable that no one would willingly molest him. The height of his racial ambition is to be so bumpy and spiny that no bird, however rash, would dare to touch him. His coloring now is pale olive, with a large white blotch in the middle so as to make him resemble a bit of bird-lime on a leaf. Not only in color and shape is he ugly, but he seeks to intimidate by his movements any approaching enemy. When he walks his head trembles as if he had the palsy, making the whole leaf quake and likewise the heart of the foe. If he is attacked or disturbed, he will fly into a tremendous rage and swing his head from one side to the other in a ferocious fashion. Mr. Scudder saw two of the caterpillars meet, and each began a great swinging of the head, hitting the other several times during this family jar. When fully grown the caterpillar, if disturbed, moves his head around in a circle on the leaf and "gnashes his teeth" in fury. To one who understands him this is a very funny bluff; for he is not only absolutely harmless, but he is also very fastidious about his food and could not be induced to take a bite out of an assailant.
When the Viceroy changes to a chrysalis he is almost as grotesque in form as when he was a larva; for he now wears a large excrescence in front that bears a resemblance to a Roman nose (Fig. 23). The obvious use of this protuberance is to convince a bird of the utter futility of attempting to swallow such an uneven morsel.
About a month after the egg s laid the adult insect appears, and on gorgeous wings sails off to join its fellow; for this is a social butterfly and is fond of dancing about in the air with its comrades.
Very soon are the eggs laid for another brood. But the history of an individual of this generation is very different in some particulars than the one just related. After the larva of the second brood hatches, he feeds, as did his parent, on the tip of the leaf, leaving the midrib for a perch during the day. But when he is about one-third grown he commences to display a peculiar interest in a certain, chosen leaf. He first fastens the petiole to the branch by weaving around the two many strands of silk; this is to keep the leaf from falling when assailed by the fierce wings of autumn. He then proceeds to the tip of the leaf and gnaws it off squarely across, leaving the midrib bare as usual; he is a clever engineer and leaves just enough of the leaf to suit his purpose. He folds the remaining portion of the leaf into a tube and sews it with a neat silken seam and then lines the tube luxuriously with silk (Fig. 21, B). This little house thus made is just large enough for the insect's body; and he crawls into it, his warty last segment fitting nicely the orifice and constituting a living door. The question at once suggests itself, how does this larva know how to do this thing? His parents did not do it, and if he inherited the knowledge it must have been from his grandparents. This is one of the inscrutable mysteries; and all we know about it is that during the warm days of autumn, long before there is any hint of winter in even the skies, this caterpillar, which never experienced a winter and whose parents never experienced a winter, builds himself this winter house and hides himself within it. Moreover, he selects a leaf near the ground so that he may have the protection of a cover of snow, which proves him to be truly winter-wise. He and all his generation pass the winter safely in their tiny tenements, remaining there dormant until the first bud or catkins of the spring call them to a vernal breakfast; then they back out of their dwellings and devote themselves thereafter to eating and growing as if they had never experienced a winter vacation while pursuing this important business. They change to butterflies in June.
The flight of the Viceroys consists of a few rapid flutters of the wings and then a period of sailing through the air with wings extended. This exposes them mercilessly to the attack of birds which regard most butterflies as the most delectable sort of food. This butterfly is especially agreeable as a diet to birds, and yet they rarely touch it. Why is this? It is another instance of the marvelous adaptation of this species to its environment, and of its power to seize an advantage in a precarious situation. This wonderful little creature that resembled disagreeable things when it was young to save itself from being eaten by birds, now, when grown, resembles in color and markings a butterfly which birds avoid for good reason. This butterfly (Anosia plexippus) is named the Monarch, and it belongs to a group all members of which are nauseous to birds. Its gay color, orange-red marked with black borders and veins, is its protection; for it is an advertisement, a sort of a poster which proclaims that here is something that right-minded birds leave alone. So our palatable Viceroy has developed colors and markings so nearly like the unpalatable Monarch that no feathered creature will touch him, unless perchance one shall be knowing enough to notice the black band across the Viceroy's hind wings which is his chief distinguishing mark.
To understand the magnitude of the feat accomplished by the Viceroys in abjuring their family colors of black, white, and blue, and adopting the orange and black uniform of the Monarchs we must consider the vast differences in the earlier stages of the two species. The Monarch egg is laid upon the tender terminal leaves of milkweed and is quite as ornate as that of the Viceroy but of quite different pattern. When the caterpillar hatches, it pursues the same tactics as does that of the Viceroy; and for the same wise precaution eats its egg-shell. The milkweed is succulent food, and the caterpillar may mature in eleven days; when full grown it is a gay creature banded crosswise with black, yellow, and green; on the second segment of the thorax and the seventh segment of the abdomen are a pair of black, flexible, whiplike filaments. They are smug-looking caterpillars, and they are smug in spirit also, for they are permeated with a race consciousness that the more they flaunt their gay stripes to the world the less likely are they to be attacked by a prudent bird problem eliminated from the start. However, there remains the problem of parasites and, there, the black whips. When I was a child I disturbed a flock of these caterpillars resting together on the lower side of a leaf of milkweed, and I still remember the creepy fascination with which I gazed at the black and yellow ringed creatures and the waving, jerking whips lashing back and forth to frighten away ichneumons; if the real ichneumons were as frightened as I was, the caterpillars were surely safe.
The chrysalis of the Monarch is the most beautiful gem in nature's casket of living jewels. Its color is the most exquisite green, and it is enamelled with dots of shining gold; a gold far more wonderful than was ever mined by man. This ornamentation can be of no real use to the insect, and one is driven again to the conclusion that nature has so wrought this living jewel for the sake of beauty alone.
From this emerald case comes, in due time, the great red-winged butterfly; and how so large a butterfly can be packed in so small a case is nothing less than a miracle. If, perchance, the issuing butterfly is a male, then we have before us the veriest of insect dandies; he is not only trig in figure and gorgeous in color but on each hind wing he carries a sachet bag embroidered in black. He indulges in no vulgar flirting of the scented handkerchief to allure his lady-love; he simply flirts a beauteous red wing with a perfume pocket on it, and lo! she is won.
But the Monarchs have other problems of their own just because the bird problem is eliminated. For because of this immunity they spread and flourished in their native tropic America until there came the problem of more food plants, more milkweed. And thus they began pushing farther north and south during the seasons of milkweed growth. As they could not endure the northern winter they simply came north for the summer and went back for the winter. At least this is what the wise men tell us. But this northern migration is carried on in a most peculiar manner. Each mother butterfly follows the spring northward as it advances as far as she finds the milkweed sprouted. There she deposits her eggs, from which hatch individuals that carry on the journey and lay their eggs as far to the north as possible; perchance it is their children that we hear of in later summer on the shores of Hudson Bay. As cool weather approaches the Monarchs gather in vast flocks for the southward migration. These flocks are not made up of the individuals that migrated north but of their children and grandchildren. There are no old ones among them travel-wise to guide them back to Florida and the West Indies. How they know the way is beyond our imagination, unless, perhaps, there flows in their bodies tropical blood that impels them to go back where the bamboo shades the stream, and the torn banners of the banana wave on the sluggish breeze. All we know is this; the Monarchs migrate northward by generations and southward by individuals; and from Patagonia to Athabasca swings the migratory pendulum. Nor is it content with this range; the strongest flier of all the butterflies, it hesitates not to try its fortune over seas, and has been found flying bravely five hundred miles from shore. Either by flight or as stowaways in vessels they have pressed eastward to western Europe and westward to the farthest isles of the Pacific. Well it is named the "Monarch," for it is the most daring and indomitable butterfly that we know, pushing back its geographical boundaries to the very edge of the Arctic zone, and exploring on leisurely and confident wing the seas that wash the shores of the Occident and Orient.
No wonder the Viceroy chose so splendid a creature to imitate. But I fear there is little noble ambition as a motive to the imitation; just to keep alive as a species is all. The value of such mimicry seems a part of parcel of the Viceroy's equipment with which to march in the ranks of the fittest. In southern Florida a common butterfly is a species of the bad-tasting family to which the Monarch belongs; this is a dark mahogany-brown butterfly with no black veins and borders. Therefore, in Florida, our imitative Viceroy doffs his stolen uniform of orange and black and dons another stolen uniform of mahogany-brown. He evidently chooses his liveries for safety and not for their intrinsic beauty; and he is entirely satisfied as long as he successfully masquerades in a guise that shall deceive the keen eyes of the birds of the air.