MIMICRY. Many butterflies of the group Heli conithe are associated with species of Leptalis belonging to another faunil• (Pierida) which copy the helieonid butterflies in form and color, and which, probably owing to a bad odor secreted by glands in the end of the body, are distasteful to birds. It is supposed by Bates, Wallace, Dar win, and others that were not the mimics dis guised as heliconias they would be devoured by birds and thus become extinct. These authors believe that the resemblance has been brought about by natural selection. In his "Contributions to an Insect Fauna of the Amazon Valley," Henry Walter Bates calls attention to the fact that a large number of the species of Heliconithe "are accompanied in the districts they inhabit by other species which counterfeit them." Ac cording to Fritz Miiller (although Bates states the same idea). the species serving as the model, being unpalatable to birds on account of its re pulsive taste and odor, is therefore safe from its foes, while the mimic, which has no bad taste or odor, is protected from attack. Mr. Bates's own views are moderate compared with those of Wal lace and later extreme advocates of Darwinian mimicry. In his original essay Bates shows that the majority of the species of Heti conidT have very limited ranges, and con tends that the cause of the formation of the local varieties is "the direct action of phys ical conditions on the individuals." Several entomologists, Elves, Packard and others, have not accepted the hypothesis of Bates and Mtiller, that the mimicry is due to natural selection, but bold that the mimicry is accidental and due to convergence to similarities in the environment. The markings, such as similar hues in models and mimics, bars and spots, Packard believes are due to such effects of light and shade, moist ure and temperature, as have produced them in birds, mammals, and reptiles. They may be perpet uated and preserved by natural selection, but the primary cause of this originally is the action of the physical agents mentioned, or at least environ mental causes affecting both models and mimics. Much stress is laid on the attacks of birds in bring ing about or aiding the process of natural selection of these markings. It is, however, to be observed that neither Bates, Muller, nor Wallace, all of whom lived for many years in the tropics, has ever seen a bird chase and devour butterflies. In fact, only a few insvetivorous birds catch butter flies or care to chase them. After several years'
special research on the habits of sparrows and other insectivorous birds, Judd states in a report to the United States Department of Agriculture that be does not know of any kind of bird "that feeds upon butterflies during any month of the year to the extent of one-tenth of one per cent. of its food." It thus appears from a comprehensive survey of the markings of animals of different classes, living both in the sea and on land, that the causes of the similarity in their markings are due to the effects of light and shade, also perhaps to moist ure—at all events to the action of the surround ings. It should also be borne in mind that the range of primary colors is not very great, nor of stripes and bars; under similar physical condi tions the colors and spots and stripes and their location on the body are repeated in animals of different groups and species. Nature is limited in the disposal of ornamental features. • Hence models and mimics may be protectively orna mented with the same hues and patterns, and it is probable that selection and the attacks of birds and lizards have had little to do with the origination of protective coloration.
BIBLIOGRAPHY. Darwin, Origin of Species Bibliography. Darwin, Origin of Species (London, 1859), Descent of Man (ib. 1S74) ; Wal lace, Daneinisms (New York, 1889) ; Bates, "Con tributions to an Insect Fauna of the Amazon Valley. Lepidoptera: Heliconithe," Transactions Linnean Socicty of London, vol. xxiii. (1862) ; Packard, Half Hours With Insects (Boston, 1877) ; Scudder. Butterflies of the Eastern United States (ib., 1887-89) ; _Milner, Transactions of the Entomological Society (London, 1879) : Poul ton, The Colors of Animals (New York, 1890) ; Bedard, Animal Coloration (ib., 1895) ; Belt, The :Vaturalist in Nicaragua (London, 1S74) ; Morgan, Animal Life and Intelligence (ib., 1800 91 ) ; Eimer, Organic Evolution (ib., 1890) ; Marshall and Poulton, "Bionomics of South African Insects." Transact ions Entomological Society of London, 1J92; Fischer, "Weitere Untersuchungen tiber die Vererbung erwor better Eigenschaften." A ligemcine Zeitsch rift fife Entomologic, vol. vii. (1892.) : Piepers, .Iffariery, .Sclekt ion, Danrin ism us I Leyden. 1903) ; with the writings of Weismann. Trimen, Cope, Meldola, Haase. Von Linden, Sokolowsky, Port chinsky. Riley. Weir. Semper, Von Wattenwyl, Schroder. Butler, Distant, Zen neck. Werner, Escherich, Peckham. Hickson, Herdman.