FIG. 36.-LIFE HISTORY OF TYPICAL MOTH. AUSTRALIA ous lepidopterous enemy of the cotton plant, found in many lands; and Hypatinia pulverea which is destructive to lac cultivation in India. In the Plutellidae the diamond-back moth (Plutella maculi pennis) is one of the widest distributed of all moths and very destructive to cruciferous vegetables. The great group known commonly as the Tortrices include many species harmful to fruit trees, and its most notable representative is the codling moth (Cydia pomonella) of the apple; Tortrix viridana is a serious defoliator of the oak in Europe, and species of Evetria are very in jurious to conifers. Mention needs also to be made of the oriental peach moth (Las peyresia molesta) which, since 1916, has become a dangerous enemy of plum, cherry, peach and apple in the United States, where it is believed to have been introduced from Japan. Of the Pyralidae the cosmopolitan Pyralis farinalis forms silken galleries among stored corn and flour; while' the most injurious of the Pyraustidae is the European corn-borer (Pyrausta nubilalis) which, since its entry into North America, has become a most dangerous enemy to maize both in the United States and Canada. In the Cram bidae the borer moth (Diatraea saccha ralis) is one of the chief pests of sugar-cane in the Gulf states and Central America. Among the Phycitidae are two moths in festing stored foods, viz., the cosmopolitan Mediterranean flour moth (Ephestia kuhniella), which is troublesome in flour mills, and the Indian meal moth (Plodia interpunctella), which is a pest of almonds, groceries and other stored goods ; both species have become practically world-wide through commerce. Among the Noctuidae, larvae of Agrotis, Noctua and other genera are known as cut-worms which feed at night, cutting off crop plants before they are very far grown. The army-worm (Cirphis unipuncta),
found throughout the United States east of the Rocky mountains and also in other countries, appears in some years in vast numbers in the caterpillar stage. The name is given from the fact that when these larvae have destroyed the vegetation in the area where the eggs were laid they advance in army-like swarms to other fields. In Europe the antler moth (Clzaraeas graminis) behaves in a similar fashion, and the last serious out break in Great Britain took place in 1917. The Lymantriidae in clude several well-known defoli ators of forest and shade trees, as has been previously men tioned ; while among the Geome trina group the looper caterpil lars of many species are injurious to fruit trees and bushes.
As an offset to the injurious propensities of so many species, certain members of the families Bombycidae and Saturniidae are commercially valuable in yielding silk. The common silk-worm moth (Bombyx mori), which belongs to the first mentioned family, is native to China and has been introduced into many countries. The usual food of its caterpillars is the leaves of the mulberry and the silk produced is of the highest quality. Among the Saturniidae several eastern species yield lower grades of commercial silk, and the varieties of the latter, known as Shantung, Tussore, Eri and Muga silks, are produced by species of Antheraea and Philosamia. (See SILK.) Very few other Lepidop tera are in any sense useful to man, excepting the showy coloured species which are utilized for ornamentation or mounted for pur poses of display. Mention needs also to be made of the caterpillars of a few species which prey upon aphides or scale insects, and thereby confer benefit by destroying noxious and pestiferous forms of insect life.