HOMOPTERA 



423 



the gall is an excrescence resembling a cock's conib in form, which 

 rises abruptly from the upper surface of the leaf (Fig. 493, a). It is 

 compressed, and has its sides wrinkled perpendicularly and its summit 

 irregularly gashed and toothed. It opens on the under side of the 

 leaf by a long slit-like orifice. 



The winter eggs can be found during the winter in the crevices 

 of the bark of the elm; each egg is usually enclosed in the dry skin 

 of the oviparous female (Fig. 493 ,b). In the spring the stem-mothers 



^t=C?F^ 



Fig. 493. — Colopha ulmicola: a, leaf showing galls from above and beneath; b, 

 fertilized egg surrounded by the skin of the female; c, newly born young of the 



■ second generation; h, its antenna; d, full-grown nymph of the second genera- 

 tion; e, adult of second generation ; /, antenna of migrant ; g, antenna of stem- 

 mother. (From Riley.) 



pass to the leaves and each causes by its attack the growth of a gall. 

 The second generation is produced within the gall; it consists of 

 winged agamic females (Fig. 493, e). These migrants can be dis- 

 tinguished from those of the other cockscomb elm-gall aphid by the 

 fact that in this species vein M of the fore wings is forked. 



The migrants of this species pass from the elm to certain grasses, 

 among them species of Eragrostis and Panicum. The forms found on 

 these secondary hosts have been described under the name Colopha 

 eragrostidis , but this is a much later name than Colopha ulmtcola. 



