16 



beyond the front: lliird joint nsnally ratlior short, conical, often partly indis- 

 tinj^uishahle from (he second on a('connt ol" the projecling hairs of the latter. 



Tile wiiiifs are large compared with the slight, feeble l)ody. The fore 

 wings are triangular, the outer edge being nearly, sometimes cpiite, as long as 

 the inner edge ; ajjcx often acute, subtalcate, or markedly talcate ; inner angle 

 di.stinct; costal edge straight, or considerably curved or sinuous. Hind wings, 

 with tlie inner edge long and straight, longer than the outer, the latter full and 

 rounded, often angular, sometimes remarkal:)ly so. Venation: usually six sub- 

 costal venules; always but three median venules ; no sul)median vein, some- 

 times a fold representing it. A subcostal ccJ! often present, sometimes two; 

 the cell being formed, almost invariaidy, by the anastomo-sis of the first sub- 

 costal venule witii its vein. Independent vein well marked; usually in the 

 middle of (he discal space. 



The legs are always long and slender; in only one genus (Lif/iosfegc) 

 are the short and stout for<' tibia; armed with a heavy, acute spine. The hind 

 legs are long and slender ; the liind 1il)ia^, nearly always long and slender, often 

 swollen, \\ith two pairs of slightly unecpial, long, slender spurs; sometimes 

 tliere is but one pair, very rarely none at all. Occasionally the hind tibias 

 have a long tuft of hairs (scales) appressed to the joint. Hind tarsi usually long 

 and slender, often a little longer than the tibia ; sometimes (as in Acidalia 

 and a few other genera) tiiey are not more than half as long as the tibijB. 



Aljdomen long and slender, usually with a well-marked tuft of hairs at 

 the end ; sometimes with lateral and dorsal sliglit tufts, and dorsal spots or 

 lateral lines. 



The genital armature is large and well developed, but varying greatly in 

 the ditierent genera. The supra-anal plate is more or less triangular, varying 

 much in size; the recurved spine is usually long and recurved; the lateral 

 claspers are usually broad, spatulate, and simple. 



Larva slender, with usually but two pairs of abdominal legs, rarely three 

 or l(>ur pairs, so that it has a looping gait. The larva live free, except in 

 certain species oi' Eupithecta, which hore in seeds. Pupa slender, often green 

 or variegated in color, inclosed in a slight, silken cocoon or subterranean cell. 



§ 4. — COMPAKATIVK AnATOMY OF THE HeAD. 



The head in tlie imago of the Lepidoptera consistsi)f tiiree pieces: first, 

 the basal or occiput; second, an intermediate piece, the. epicranium ; and 



