ENGLISH: ILLINOIS TREES: THEIR INSECT ENEMIES 



Fig. 5. — Oystershell scale: an infestation on a twig. A sapsucking in- 

 sect is beneath each brownish shell. An infestation of this common and 

 destructive insect may kill twigs and branches of lilac and other plants. 



The overwintering, pearly white eggs of the oystershell 

 scale hatch about the latter part of May, the time varying with 

 weather and latitude. Each young scale, called a crawler, moves 

 from beneath the mother shell and crawls about, usually toward 

 younger wood. After a short time the crawler settles, loses its 

 legs and antennae, and starts making a shell covering. The cov- 

 ering is enlarged from time to time to accommodate the grow- 

 ing insect. The male scale develops wings, escapes from the 

 shell by squeezing under the edge, and roams freely for a mate. 

 The female does not leave her shell for the mating event, but 

 keeps sucking away at the tree sap. Under her shell she lays 

 80 to 100 eggs, which hatch the following spring. 



Control Measure 5 (end of circular) in late winter. Con- 

 trol Measure 3 about the first of June, after eggs hatch. Thor- 

 ough spray coverage is essential. 



Fall Webworm, Hyphantria cunea (Drury), fig. 6. — Un- 

 sightly webs enclosing one or more branches of an ash in the 

 early fall are signs of a ravenous colony of hairy caterpillars of 

 the kind commonly known as the fall webworm. The adult fe- 

 male of the fall webworm, a satiny white moth, emerges from 

 one of the overwintering cocoons in early summer, mates, flies 

 into a suitable tree, and deposits a patch of several hundred 

 greenish eggs, usually on the under side of a leaf. On hatching, 

 the young caterpillars move as a group to the upper sides of 

 leaves and start feeding. At the same time, they start spinning 



