Among the most re markable departures from the usual life-history prevalent in Lepidoptera is that afforded by the Indo-Australian Lycaenid butterfly, Liphyra brassolis, whose larva is flattened and cov ered by a hard cuticle, devoid of evident segmentation. It is found in association with the ant Oeco phylla smaragdina and is be lieved to prey upon the brood of the latter, its hard covering serv ing as a protection against the ants. Pupation occurs in the old larval skin which forms a pupa rium loosely enclosing the chrys alis within. The newly emerged butterfly is covered with loosely attached white scales, over its orange and brown ordinary scales, which serve as protection against the ants, since they fall off readily and cause those insects evident discomfort if they adhere to them. Another very interest ing species is the North American yucca moth Tegeticula alba, the females of which have the maxillae provided with a long tentacle specially adapted for collecting the pollen of yucca flowers. After collecting a large mass of pollen she inserts her eggs deep into the ovary of a flower, usually other than that from which the pollen was gathered. After egg-laying she then thrusts the pollen into the stigmatic opening of the flower. By means of this provision the development of the seeds upon which the larvae feed is ensured and any not so devoured secure the perpetuation of the yucca. A third example is afforded by aquatic moths of the genus Acentropus. The young larvae live submerged in mines which they excavate in the leaves of water plants ; as they grow older they form tun nels of spun leaves and the sub merged pupa is enclosed in a similar shelter. The female moths are dimorphic : the long-winged forms are aerial, while those with reduced wings are aquatic, using their alary organs for swimming.
A few Lepidoptera possess a capacity for sound-production. The death's head moths (Acherontia) have long been known to emit a shrill chirping note. The method of its production has been much discussed and it is believed to be caused by the forcing of air through the haustellum. The cat erpillar also has been noted to produce sharp cracking notes re sembling those emitted during the discharge of successive electric sparks ; in this case the sound is brought about by bringing the mandibles forcibly together. Sev eral moths are able to stridulate, and in certain Agaristidae the male has a corrugated area beneath the costa of the fore wings, and the membrane in that area is distended to form a resonator. It is suggested that the clicking -- sound observed is caused by the ridged area on the fore wings rubbing against spines on the legs during flight.
Geographical Distribution. —Lepidoptera have a range prac tically co-extensive with that of flowering plants and are only ab sent from the remote and inhos pitable regions around the poles. Among butterflies it is interest ing to note that at least 46 spe cies extend within the Arctic Circle and some range as far north as 80° lat. ; but, on the other hand, no resident butterfly is known from Iceland. In the Antarctic, 50° lat. is about their most southerly limit, which is reached by a species of fritillary found on an island near Cape Horn. Some species of Lepidop tera are almost world-wide and exhibit migratory tendencies, notable examples being the hawk moth Celerio lineata and the but terfly Pyrameis cardui, the latter being found in all the continents excepting South America. Sev eral Noctuid moths, notably Agrotis ypsilon and Chloridea obsolete, are now cosmopolitan. The blue butterfly Lampides boeticus occurs over all the warmer parts of the old world to Australia as well as reaching remote islands in the Atlantic, Pacific and Indian oceans. In some cases human agencies have possibly been partially responsible for the wide range enjoyed by such insects by the introduction of suitable food-plants in regions where they did not previously exist. While many of
the largest families of Lepidoptera are cosmopolitan, certain others are limited to definite areas of the globe. Among moths the Xyloryctidae are almost limited to Australia, the Lacoso midae are confined to the western hemisphere and the Megalopy gidae have few species elsewhere. Among butterflies, the sub families Ithomiinae, Brassolinae and Heliconiinae of the Nymph alidae are confined to South America, and Acraeinae are mainly centred in Africa. The richest fauna of Lepidoptera, as in most orders of insects, is found in the tropics, and Brazil probably yields more species of butterflies than any other part of the world, over 600 species having been stated to have been taken within an hour's journey of the city of Para alone. Some idea of this wealth of species will be gath ered when it is mentioned that only 70 species are recorded from the British Isles.
Some species of Lepidoptera have a marked capacity for migrating from one region to another, either individu ally or in swarms. In North America great companies of the monarch butterfly (Danais archippus) form in parts of Canada and the northern United States and fly southwards in early autumn, apparently reaching the Gulf states; in June and July this butterfly appears in the northern states and the individuals then seen are believed to be re-migrants from the south. In Ceylon C. B. Williams mentions that about 69, out of a total of
species of butterflies known in Ceylon, have been recorded as taking part in migratory flights. The latter occur at the beginning and at the end of the north-east monsoon and proceed in various directions. At times these flights seem to bear some correlation with seasonal changes and it has been sug gested that they originate owing to the dry ing up of the food-plants, but the data is at present insufficient for drawing reliable conclusions. The painted lady (Pyrameis cardui) moves northward in spring in north Africa and south Europe, invading most of central and northern Europe as far as Iceland; individuals found in countries such as England and Germany are entirely emigrants from the south and, in some years, they fail to appear. Migratory - swarms of Lepidoptera have often been
recorded from far out in the ocean. In one case a swarm of the weak-flying moth Deiopeia pulchella was observed at sea nearly I,000 miles from its nearest known habitat. Solitary individuals of various species often fly on board ship at a great distance from land, and are chiefly those of wide geographical range.
No undoubted fossil Lepidoptera are known before the commencement of the Tertiary period, although it is probable that the primitive Homoneura existed at an earlier epoch. Butterfly remains are known from the Eocene and Oligocene of North America and a few moths have been described from Baltic amber. As a whole, knowledge of the fossil history of Lepidoptera is very scanty, which perhaps is scarcely surprising considering the delicacy of structure exhibited in so many of the species.
In the caterpillar stages a large number of species of the order are injurious to crops and forest trees. Among the Hepialidae the subterranean larvae are destruc tive to grass roots and in Aus tralia those of Leto and Charagia bore into the solid wood of trees. Other wood-borers are found in the families
including the goat and leopard moths, Xyloryctidae and Sesiidae. The Tineidae include the cosmopoli tan clothes moths, Tinea pellionella and biselliella and Trichophaga tapetiella, which are destructive in houses, their larvae attacking wool, hair, carpets, feathers and dried skins. Among the Gelechi idae are the Angoumois grain moth (Sitotroga cerealella) which attacks wheat, maize, etc.; Pectinophora gossypiella, the most seri