16 



beyond the fronl ; third joint usually rather short, conical, often partly indis- 

 tinguishable from the second on account of the projecting hairs ol the latter. 



The wings are large compared with the slight, feeble body. The lore 

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

 the inner edge; apex often acute, subfalcate, or markedly falcate; inner angle 

 distinct: costal edge straight, or considerably curved or sinuous. Hind wings, 

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

 rounded, often angular, sometimes remarkably so. Venation: usually six sub- 

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

 limes a fold representing it. A subcostal ceil often present, sometimes two; 

 the cell being formed, almost invariably, by the anastomosis of the first sub- 

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

 middle of the discal space. 



The le«s are always long and slender; in only one genus (Litkostege) 

 are the short and stout fore tibiae armed with a heavy, acute spine. The hind 

 legs are long and slender ; the hind tibiae nearly always long and slender, often 

 swollen, with two pairs of slightly unequal, long, slender spurs; sometimes 

 there is but one pair, \rry rarely none at all. Occasionally the hind tibia? 

 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) they are not more than half as long as the tibiae. 



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

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

 lateral lines. 



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

 the different 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 four pairs, so that it has a looping gait. The larvae live free, except in 

 certain species of Eupithecia, which bore in seeds. Pupa slender, often green 

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



§ 4. — Comparative Anatomy of the Head. 



The head in the imago of the Lepidoptera consists of three pieces: first, 

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



