INSECT PESTS OF OHIO SHADE AND FOREST TREES 219 



The newly-hatched larva is colored a mixture of yellow and 

 black. When mature it measures about a half-inch in length and 

 appears as indicated in Plate XXIV, Fig. 2. 



Tlie pupae are about one-fifth of an inch in length and are 

 bright orange in color. They are found in greatest quantity at the 

 b:.se of the host. 



Life history. — The adult beetle passes the winter in the shelter 

 of attics, in piles of rubbish, or in any other protected place which 

 is not too damp. With the development of tree foliage in the 

 spring, it leaves its retreat and flies to the treetops where it begins 

 feeding. After a short time the eggs are deposited, and these hatch 

 in less than a week's time, whereupon the larvae begin feeding upon 

 the leaf tissues. 



From 2 to 3 weeks is required for the completion of larval 

 growth, at the end of which the larvae make their way to the 

 ground, great numbers pupating at the base of the tree, while 

 others pupate in the grass and nearby trash. 



The length of the pupal period depends in large measure upon 

 the weather. If the weather is warm, the adult emerges in 7 days, 

 but if cool, more than 3 weeks may elapse before it appears. There 

 are at least two broods a season in Ohio, and some evidence supports 

 the possibility of a third brood. 



Nature of work. — The injury caused by the elm leaf beetle 

 consists in the mutilation of the foliage of the host. This is of two 

 types. The spring work of the beetles which have hibernated is 

 characterized by holes eaten completely through the leaves as indi- 

 cated by Plate XXIV, Fig. 9. The larvae, however, attack the under- 

 surface of the leaves and chew away the epidermis, leaving a skele- 

 tonized effect as indicated by Plate XXIV, Figs. 7 and 8. As a 

 general result of the two types of feeding, the foliage becomes muti- 

 lated, brown and f unctionless ; and, if the attack is severe, the leaves 

 fall. Sometimes, after the first crop of foliage is destroyed by the 

 first brood of insects, the trees put out a second crop which in turn is 

 destroyed. Defoliation for two successive seasons, particularly if 

 dry weather prevails, is sufficient to kill the trees. 



Aside from the harm done the host, the mass of insects which 

 collect about the base of the tree is very repulsive, thus making the 

 pest further objectionable. 



Food plants. — Fortunately trees of the elm family only are 

 attacked by this pest. Of the elms, the European varieties suffer 

 most severely, but in the absence of the favored host other elms are 



