If Pieris rapae was a colonizer, not a migrator, the monarch butterfly was the real thing, migrating south in the fall and back again in the spring. Scudder named it the monarch (rejecting “storm butterfly” and “milkweed butterfly,” among other names) and helped lead the first investigation of its movements, variations of which have continued to this day, with literature more vast than that on any other butterfly.47 Monarchs must have been flying back and forth for many years, but not until the 1860s and ’70s, after Americans had embraced Western natural history that created a context (context is all, after all) in which looking at such things made sense, did Americans suddenly begin to observe the monarch’s habits. Everywhere men and women reported monarchs flying by the millions in September in gigantic, undulating waves extending for miles; like the passenger pigeon migrations of the age, these swarms sometimes obscured the sun, blurring day into night.48 Monarchs still migrate this way, but nowhere near as phenomenally as in the nineteenth century.
Unlike Edwards, Grote, Scudder, and Strecker, Charles Valentine Riley was an insect generalist throughout his career. But he did original work on butterflies, including being the first to describe the monarch’s life history, in 1868, in the American Entomologist, which he edited with Benjamin Walsh. He was also the first to see, if with limited proof, that the butterfly traveled south and returned in the spring. Scudder stated his own views in his life history of the insect in The Butterflies of the Eastern U.S. and Canada and in his essay “The Swarming and Migration of Butterflies.” “I believe,” he wrote, “there is over the entire extent of the country inhabited by it, at least east of the Rocky Mountains and north of the Gulf States, periodic movement of the butterfly, in the south in the season which corresponds to the end of September in New England, and to the north in the time of the first season of egg laying.”49 He based his conclusion on the ample evidence he received in response to the hundreds of letters he sent out to “many intelligent observers stationed” around the country. “I find that the milkweed butterfly is beginning to swarm this autumn,” he wrote his friend Charles Fernald in Maine. “Could you send a few statistics on the point, such as an estimate of the numbers seen within a given period; the general direction taken by the butterflies; how much variation there appeared to be from that direction; whether there was any reversal of direction,” and so forth. “It only needs that you should have your weather eye out.” At the same time, Scudder called for “systematic and concerted study over a wide extent of territory before a satisfactory solution can be expected” (not achieved, however, until the 1970s, nearly one hundred years later). Scudder believed that the monarch lived longer than any other butterfly (up to sixteen months) and that, in New England (and everywhere else as well), it was mainly single-brooded. But that, too, begged for more “systematic and concerted study.”50
Not everyone agreed that the monarch migrated south, like the birds. Edwards, for all his observational acumen, thought the idea ludicrous, ridiculing Scudder for even considering it and for generalizing, as he so often did, Edwards charged, on the basis of “one or two facts.” Rather, the monarch hibernated where it was born and bred (so to speak), going nowhere; it had a short life, said Edwards, like every other butterfly, three or four weeks, with the exception of insects that hibernated as larvae, eggs, or pupae. Moreover, the monarch was not single-brooded, as Scudder contended, but in places like Edwards’s home, the Kanawha Valley, of West Virginia, triple-brooded, and elsewhere possibly “more-brooded.” One shouldn’t generalize, he insisted. In the end, Edwards proved Scudder wrong about only one thing: the number of monarch broods, a mistake Scudder conceded.51 On the other questions, Scudder proved victorious (although Edwards may have never acknowledged it). Many adult butterflies did live longer than three or four weeks, and, of course, the monarch migrated. While other butterflies died from the impact of icy cold, this butterfly, for some unknown reason, had learned to adapt by going south.
Of all the trickery evolved by butterflies to survive, none aroused naturalists’ curiosity more than the way they modified their bodies and wings to frighten or mislead their predators. Many hid from view under rocks or brush, in holes or nests. Alarmed by something, they might drop to the ground and “feign death,” as Grote suggested, although he preferred the phrase “keep still,” since lepidoptera, like other animals, had no idea what death was and could hardly “feign” it.52 (“Whether insects can have any knowledge of death, as such,” Grote observed, “may be a matter of opinion, but I would as soon credit them with a knowledge of history.”)53
Butterflies also sometimes “swarmed” or “assembled” in ways to bewilder or confuse, as Grote put it, or, being “shy,” appeared in public infrequently, ready to flee into the shadows at the least hint of danger, as Will Doherty speculated.54 Many species used “Timidity as a Source of Protection,” Doherty observed in a letter to his mother, wondering why Darwin and Wallace had “left” this “subject untouched.” “You see in cold countries,” he explained, “the struggle for existence is chiefly carried on against adverse climate; the cold weather kills ten butterflies where their enemies kill one. But in tropical climates animals chiefly have each other to contend against. They are always chasing or chased.” Several butterflies, almost “dying out,” had survived by “being shy,” he noted. “They are peculiar to these hills [the Kanan Devan Hills in southwest India] and are exceedingly timid and hard to catch.”55
But butterflies found even better ways to deceive: they acquired the ability to mimic the forms, shapes, and colors in the natural world around them, so far as to change, over extremely long periods of time, the very character of their physical identity. Mimicry is most commonly found in insects rather than in other animals, and has been most often studied in butterflies, the term itself first appearing in the 1815 Introduction to Entomology, by William Kirby and William Spence.56 No naturalist took the subject seriously, however, until Henry Bates, the English explorer and naturalist, propounded, in 1866, the first and most enduring theory of it, fruit of his fourteen years on the Amazon River and his study of numerous tropical butterflies and profoundly influenced by his understanding of Darwin’s theory of natural selection. Bates observed that many palatable species, attractive to predators, gain protection from their enemies by successfully imitating or mimicking unpalatable butterfly species. But how did such a remarkable thing occur in nature? And how, moreover, did some species succeed in their resemblances, while others similar to them and living in the same locality did not? The answer: “Natural selection, the selecting agents being insectivorous animals”—and these could be anything from birds and lizards to other insects—“which gradually destroy those varieties that are not sufficiently like unpalatable” forms to elude predation.
“When the persecution of a variable form is long continued, the indeterminate variations naturally become extinct; nothing remains in that locality but the one exact counterfeit.” The insectivorous animals, in other words, actually do the work of God by “destroying variations unsuitable to the locality” or for survival, thereby allowing the fit or successful butterfly counterfeiters—or those immune to predation—to emerge, thrive, and reproduce.57
Bates’s breakthrough essay, with its unprecedented empirical proof of a theory that Darwin himself had not effectively demonstrated, released a wave of thinking on mimicry throughout the West and the far reaches of the Western empire—in South Africa, with the work of Roland Trimen; in British India, with the studies of Lionel de Nicéville, Major G. F. L. Marshall, and James Wood-Mason; and, in Nicaragua, where the British gold mine engineer Thomas Belt, reporting on mine practices, analyzed the mimicry of the heliconian butterflies.58 In England itself, Alfred Russel Wallace observed, among other things, that females won most by imitation (“probably due to their slower flight, when laden with eggs”) and that the bright colors of many insects served as warning signals to predators to back off or suffer the consequences. Another Englishman, Edward Poulton, endowed Wall
ace’s warning concept with a name: aposematic (derived from Greek apo, or “away,” and sematic, or “sign”), a term widely used today; he proved, with a series of light experiments, how readily chrysalids mimicked the colors of their background. Scudder wrote that Poulton obtained “almost at will chrysalids of different colors, according to the tints with which he has surrounded them, and so has opened a new field of experimental inquiry.”59 An ardent Darwinian, Poulton believed that “the principle of Natural Selection explains the origin of all appearances except those which are due to the subordinate principle of Sexual Selection.”60
Americans, too, were influenced by Bates’s mimicry theory, which goes far to explain why they were so interested in predators, singling them out for their selecting abilities. Like Darwin and Bates, American butterfly people saw nature as a chaotic whole, generating over millions of years a staggering community of organisms, some strong enough as species to withstand the fiercest buffeting. The American interest in mimicry began in the late 1860s, with Charles Valentine Riley, who wrote about it in his own American Entomologist, and continuing through the 1890s with Abbott Thayer, who invented a “beautiful new law” in nature: “countershading” or “obliterative shading,” whereby many animals produced a misleading blend of colors, shapes, and lines. A collector of tropical insects in his youth and a Darwinian like Riley, the Yankee Thayer wrote adeptly of mimicry in larvae and adult imagoes, at the same time criticizing the concept as too limited to explain how nature “protected” animals from predators. Influenced by Poulton’s thesis that “natural selection dictated that all animal coloration prove useful,” he proposed, instead, a law of “obliterative coloration,” which asserted that all butterflies (not merely the inconspicuous ones) elude their enemies because their “surfaces” reflect the patterns and colors of their backgrounds, “causing them to pass for empty spaces through which the background is seen.”61
In the time between Riley and Thayer, other Americans were studying how butterflies and moths at every stage of the life cycle imitated the world around them to deceive what preyed on them. The underwings of many American butterflies were notorious for mimicking leaves, as American naturalists pointed out, but the entire wing surface often mimicked the background. Grote, drawing on the work of the American D. S. Kellicott, described the moth Rhodophora florida’s imitating “the withering blossoms of the Common Evening Primrose,” hiding during the day by copying, exactly, the colors (yellow and pink) of the flower. “Sometimes,” Grote reported, “the pink of the wings is not wholly covered but the tone of the continuous colors is such that the harmony is complete.”62 Caterpillars, such as those of the spanner moths, the hawk moths, and the bagworms, misled predators by looking like leaves, as Joseph Lintner and Grote observed. “When discovered, a little colony were hanging head downwards,” wrote Grote of the spanner species, and “were remarkable for mimicry of withered leaves.”63 Pupae, Scudder noted, such as those of the giant swallowtail and the falcate orangetip, reflected the surrounding world, the former with the appearance of “a broken bit of rough bark,” the latter disguised as a “doubly sharpened stick.”64
Butterflies protected themselves, too, by mimicking other organisms, from insects to birds. Herbert Smith, a young American explorer from Manlius, New York, who would nearly equal Will Doherty in his skill as a tropical butterfly collector, first encountered this copying in the Brazilian forests; Smith had a collection of such mimics packed away in closets in his Brooklyn apartment and, in the late 1880s, offered the collection to the Museum of Comparative Zoology. Beetles and moths that “mimicked wasps,” “ants that mimic bees,” and “butterflies and moths that mimic Heliconians” were included. “I have myself made special study of these forms,” he told Samuel Henshaw of the Museum.65 So had Doherty in India, observing butterfly ocelli, or eyespots, in the Kumaon region; they formed on the wings during the wet season and replicated, apparently, the eyes of owls and other predators. Ocellation protected butterflies “during the rains when insectivorous birds” were “especially numerous.”66 Near Rangoon, Doherty caught a species of Thaumantis that “mimicked when flying a large cicada. It swarms also in Borneo, where I have often mistaken [it] for the cicada, and vice versa.”67
Scudder probably wrote more about mimicry and protective resemblance in the 1880s than anyone in America—another indication that he had turned away from Agassiz on matters of evolution. In his many life histories and essays, he observed how concealment and deception functioned in the butterfly life cycle. Thus, female butterflies sometimes laid only a few eggs to escape predators, or the eggs themselves duped ichneumons and other parasitoids by growing “flexible filaments” or hairs “so that the poor bewildered madame must struggle through a weary chaparral before she can attain the barren grounds at the summit and find a spot to readily insert her sting.” At the caterpillar stage, the butterfly was driven by the need to “conceal,” resorting to feeding at night and hiding by day, dropping to the ground and curling up when frightened, and moving “rapidly in motion forward and backward” to frighten interlopers; at different molts and in the pupal stage, the insect might look like “a lump of bird dung,” discouraging birds from picking it off.68
Most interestingly, a few North American butterflies resembled other butterfly species in appearance, notably the viceroy butterfly, an orange-and-black insect that copied the monarch, a noxious insect avoided by birds and other similar predators (see color plate 4). Scudder coincidentally coined both vernacular names, monarch and viceroy, the second species, according to him, belonging to the genus Basilarchia (that term failed to stick; today the accepted generic grouping is Limenitis). This genus contained two other well-known eastern species besides the viceroy: the red-spotted purple, flying in the southern part of the range, and the white admiral, in the north, especially in New England (at least, Scudder thought they were separate species; today, experts think otherwise).69 The red-spotted, in particular, was one of the most sought-after butterflies by novice collectors, as well as hard to catch. “Well do I remember a chase for this butterfly,” recalled Frederick Clarkson of New York City in 1885, “the first that I had ever seen on the wing. It was a royal game of tag, with hide-and-seek variations. We see-sawed up and down a ravine for nearly an hour. By the time I had worked my way down over the rocks and through the briers, it was spreading its wings on the bank I had just left, and when I returned it was away again to its favorite leaf on the other side. Tired and heated, I gave up the chase, when the arthemis, in a most provoking way, lit upon a shrub beneath my very nose.”70
To Scudder the purples were “the very queens of butterfly society,” especially the white admiral, which he had seen in his youth crowding roadsides and wooded paths by the thousands, and streaming into the kitchens and parlors of country homes. Though visually different, all three “species” had a great deal in common: the same kind of eggs, the same larvae and pupae, and the same wing structure; they shared so much that they belonged, indisputably, to the same genus; only color and pattern differed, although the two purples also showed a good deal of orange, in the form of spots in rows along the hind wings. These orange spots were critical, explaining how and why the viceroy butterfly split from its purple chains. Both purples, Scudder claimed, hybridized at the margins of their ranges, where, millions of years ago, their progeny began to display a growing number of red spots and to fly “in the same region and at the same time” as the monarch butterfly. Slowly, the new variant capitalized on its new color until it began to resemble the monarchs and so could “venture more often into the open country than its allies, and thus gain wider pasturage and surer assistance.” “If one has the slightest advantage in the fight of life,” Scudder wrote in “Mimicry and Protective Resemblance; or, Butterflies in Disguise,” in volume 1 of Butterflies, “how small soever this difference may be, it must, by the very laws of natural selection, be cherished, perpetuated, increased by slow but sure steps. Knowing what we know of the laws of life, mi
micry of favored races might even have been predicted.” The viceroy was a remarkable example of butterflies mimicking butterflies. It demonstrated how resourceful “natural forces” remade organisms into “protected species.”71
Scudder (along with Edwards and Grote) often commented on how butterflies and moths concealed themselves and took different forms throughout their lives, virtually the whole of their life histories marked by shifting adaptations. At every molt, a butterfly larva took a new form; so, too, many butterflies were sexually and seasonally dimorphic or polymorphic. Pupae of the same butterfly might vary in color and form. In a sense, the real identities of lepidoptera were hidden, invisible strands passing through a series of disguises. “All the metamorphoses and especially such complete changes as are undergone by a butterfly during its varied life from egg onward,” Scudder wrote in his remarkable excursus “Hypermetamorphosis in Butterflies,” “are acquired characteristics, gradually gained in the struggle for existence by adaptive devices.”72 To put it another way, the identity of butterfly species was an outgrowth or consequence of the need to defend in order to survive. That butterflies (and other similar animals) were not what they appeared to be was, in fact, what they were.
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