BUTTERFLIES. 736 BUTTERFLIES. wound round and round the l&tva, until the silken case thus made sutEces; or they may form merely the lining of an earthen cell (for many si)ccies i>upate under ground), or they may serve to bind into the cocoon their own hairs, chips of wood, or other materials, or to tie down rolled leaves, or form a web-like network luiii^ like a bag or a liammock from some supi)ort, or making a fuzzy mass in some crevice or among leaves and twigs. When the work of spinning the silk is once begun, it is carried on almost without cessation for several days. The forms of cocoons are various: when not concealed, they are usually of a tint that blends well with their surround- ings, leaving them inconspicuous, while their ma- terial is calculated to resist the attacks of insect- eating birds and mammals, or of ichneumon-ilies and other intending parasites. Cocoons are mainly the work of moths, to which the term "pupa' is now frequently restricted, for the butterllies pass their pupal stag*; incased in comparatively rigid integuments, which form a 'chrysalis.' They vary greatly in form, some being acorn-like, others very angular, etc., and most are obscure in tint, so as to be easily over- looked, but some are brilliant in color, usually of golden or metallic hues, ^hence tlie name chrysalis. Some butterfly chrysalids (Xymphali- d:p) are simply suspended from the posterior end (Suspensi); those of others (Papilionidse) are held in place by an additional strand or gir- dle of silk ( Succincti) . Within the chrysalis or cocoon is the immature butterfly or moth, and all the parts belonging to the future adult insect may be found by examination. Breathing goes on through air openings, and the parts steadily develop. "The pupae of the vast majority of moths, of butterflies, and of two-winged flies have the limbs and wings not merely pressed close to the body, but immovably fixed thereto by a general hardening and fusion of the outer skin. Such pupop are distinguished as 'obtect.' But al- though the limbs are incapable of motion, certain abdominal segments remain free, so that the hind Ijody can be, to some extent, bent and turned about : and, by means of rows of spines on the abdominal segments, the pupa is, in many cases, enabled to work its way out of its shelter, when the time for the final change has arrived." Such are styled 'incomplete.' The pupal stage may be of long or short duration. JIany Lepi- doptera pass the winter or the tropical dry sea- son as pupip. Some iiave several broods a year, and in such the pupal stage of the hibernating brood will last longer than that of the others. The Imago. — When the pupa has arrived at maturity; its coverings split and allow the emer- gence of the 'imago" or perfect insect. "Hardly anything m Ihc range of insect life," remarks Dr. W. J. Holland, "is more interesting than the rapid development of the butterfly after its first emergence from the chrysalis. . . The imago, as it first emerges, is provided with small, flac- cid wings, which, together with all the organs of sense, such as the antenn;e, require for their com- l)lete development the injection into them of the vital fluids, which, upon first emergence, are largely contained in the cavities of the thorax and abdomen. Hanging pendant on a projecting twig, or clinging to the side of a rock, the in- sect remains, fanning its wings, while by the strong process of circulation, a rajjid injection of the blood into the wings and other organs takes place, accompanied by their expansion to normal proportions, in which they gradually at- tain to more or less rigidity. . . The body is robbed of its liquid contents in a large de- gree ; the abdomen is- shortened up ; the chitinous rings which compose its external skeleton be- come set and hardened; the wings are expanded, and then the moment arrives when, on air^- pin- ions, the creature that has lived a worm-like life for weeks and months, or which has been ap- jiarently sleeping the sleep of death in its cere- ments, soars aloft in the air, the companion of the sunlight and the breezes." It is impossible here to go into any descrip- tion of buttei-flies and moths. Butterflies, as a rule, are more brilliant than moths, many of them, in the tropics, especially resplendent in metallic hues, rivaling those of the 'eyes' of peacock-plumes. Moths, on the contrary', are more usually dull of hue, and less given "to ap- pearing in open places, even when they fly by day, yet some are high-colored and beatitiful. Both butterflies and moths, and their caterpil- lars, may resemble to some extent the shape of the object or the coloration of their background, or of other insects. Thus they illustrate most strikingly and copiously various phases of 'mim- icry' and 'protective coloring.' Butterllies, like bees and many other insects, carry pollen from flower to (lower, and hence aid gieatly in the formation of seeds. See Cross- rEI!TII,IZ.TIOX. Geographical Distbibi-tion. Lepidoptera oc- cur wherever plant-life suited to the nourishment of the caterpillars is present. They are siui-loving forms, and are most numerous in species in the tropics. However, in numbers of individuals, some of the temperate zone forms far outrank any of the others. Some species occur in the Arctic zone and on the tops of snow-clad moun- tains. Certain forms flourish in the far north. in Greenland, Labrador, and Iceland, or on tops of snow-capped mountains. Some species are re- stricted by temperature or food-plant to a very limited area, while others are practically of world-wide distribution. Widely distributed forms either feed on widely distributed plants, or can feed on a number of different food-])lants. The delicacy of the Lepidoptera has prevented their common preservation as fossils. The Ter- tiary rocks of the Western United States, and the rocks from the time of the British chalk down, have yielded remains of a few scattered species. About 50.000 species of T-epidoptera are known, of which (i.OOO occur in America north of Mexico. Of skippers there are two families — the large skippers, Megathymidie, and the smaller skippers, Hesperiida'. The butterflies include the Papili- onidae, Pieridie, Lyca>nidie, and Nymphalida'. and all other families (over 40) belong to the moths. Bliu.U)(:R.pnY. For general works, see bibliog- raphy under Insects; A. Hyatt and J. !M. Arms, "Cleaning of iletamorphosis," Natural Science, nil. (London, 1896); E. B. Poulton, "Neurol- ogy of Pupa" in Transactions of the Li'tinwan- Society (London, 1800) ; T. A. Chapman, "Pupa; of Moths," in Trnnsuctions of the Entomoloiiical Society (Lcmdon, 1893); and subsequently W. F. Kirby, Haiuiboolc to European liuttcrflic.t and .Moths (with guide to literature of the order, 5 vols., London, 1895) ; S. H. Scuddcr, liuttcr/licsof Xew Enqland (3 vols., Cambridge, 1889) ; W. J. Holland, r/ie Butterfly Book (New York, 1898) ;
