OSBORN AND BALL REVIEW N. A. SPECIES OF IDIOCERUS. I 25 



Sa/ix, Populus and CmfcEgits, the different species usually being con- 

 fined to trees of a single genus and sometimes to a single species The 

 larvae usually mimic the color of some part of the tree upon which 

 they feed and are difficult to detect; they may be readily separated 

 from those of other tree-inhabiting forms by their broad heads, prom- 

 inent eyes and long roundingly tapering abdomens. 



As far as known all the species are two-brooded, the adults hiber- 

 nating and depositing eggs in spring. In the case of alternatus the 

 eggs are placed near the tip of the younger twigs, usually several in a 

 place, often causing distortion or death to the part. 



SYNOPSIS OF THE SPECIES. 



A. Crest of the vertex with two rcnmd black spots about twice farther from 

 each other than from eyes, 



B. Spots on the vertex large, ecarceiy more than their own diameter 

 from the eyes — species in which the head is very deep and the 

 pronotum arched (male antennae without discs), 

 c. Outer branch of first sector of elytra again forked, usually form- 

 ing a triangular anteapical cell before curving away to the 

 costal margin, species fulvous with light marking. 

 D. Clavus fulvous, usually a light stripe just outside the outer 



nervure, center of costa with a large black area 



maculipennis Fh 



DD. Clavus with the basal half creamy yellow, except a black 

 line along the scutellar margin, center of costa scafcely 



darkened provancheri V. D. 



CC. Outer branch of first sector of elytra usually simple, some- 

 times an oblique nervure running to the costa. Species light 

 gray with a pair of large, angular, black spots on each, pro- 

 notum and scutellum in line with those on the head 



cratcegi W D. 



BB. Spots on vertex small, two or more times their own diameter from 

 the eyes. 



C. Nervures of elytra not distinctly alternating in color, the outer 

 fork of the outer branch of first sector usually curving away 

 to the costa without forming an anteapical cell, or, at most, a 

 small triangular one. 



D. Species green, a dark line along the sutural margin of 

 elytra, nervures indistinct (male antennas without discs). 



snowi G. & B. 



DD. Species brown, the elytra milky sub-hyaline with distinct 

 tuberculate brown nervures (male antennae with discs). 



[Proc. D. A. N. S., Vol. VII.] 15 [ December i, 1898.] 



