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ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 47 



Fig. 23. — Elm cockscomb galls. Each gall contains many greenish aphids. 



elms indicate the presence of larvae of this species. Probing an 

 infested tree with a knife will disclose flat, shallow galleries run- 

 ning in many directions and white, legless, segmented grubs. 

 Each larva is about an inch long when full grown. The larva pu- 

 pates in May. The adult is a gray beetle, about one-half inch 



