34 STEIJCTUEE AND LITEEATUEE. 



of median nervules. It is variably strong and some- 

 times wanting ; I have shown how it varies in the 

 genera related to Erotyla and Spragueia. It has no 

 value in establishing the subfamilies, and its varia- 

 bility suggests that, except in a general way and in 

 relation to the shape and form of the wings, the par- 

 ticular course and appearance of the veins cannot 

 be used to establish higher groups than genera ; in 

 these latter the characters offered by the veins are 

 often convenient to use. An examination of the 

 shape of the outer corneous pieces protecting the 

 male genitalia shows that occasionally they oifer 

 peculiar shapes in different genera. The pattern 

 of the wings is sometimes peculiar, and assists in 

 the work of locating the species ; but it is, on the 

 whole, very uniform. The colours vary somewhat 

 and, in the genera allied to SeUotliis, which frequent 

 flowers in the daytime, they are often very gay. 



With regard to the immature stages, the North- 

 American Noctuidse offer several striking larval 

 forms. The caterpillar of Scm^isimemna Trisignata 

 is remarkable for its resemblance to that of the 

 Diurnal genus Basilarcliia of Mr. Scudder. The 

 larva has long, somewhat isolated thoracic hairs, 

 elevates the front of the body when at rest and, 

 when disturbed, sways the free portion from side to 

 side, which has caused it to be known as the " zig- 

 zag caterpillar." It lives on species of Syringa^ and 

 pupates by boring into the solid wood (in confine- 

 ment a piece of solid pine will serve its purpose), 

 carefully closing the orifice beliind it. Professor 

 J. Henry Comstock ('Papilio,' i. p. 147), who has 



