22 



ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 47 



winter. The wingless female climbs a nearby tree and, after mat- 

 ing, hides hundreds of eggs in crevices and under loose bark. 

 These eggs hatch just as soon as the leaf buds begin to open in 

 the spring. An elm may be partly or completely stripped of its 

 foliage by spring cankerworms. 



Control Measure 1 or 2 (end of circular) as soon as leaf buds 

 begin to open in spring, when the worms are still small. 



Fig. 15. — Elm foliage damaged by spring cankerworms. The dark green 

 to black "measuring worms" begin feeding before leaf buds are completely 

 open. 



