SHADE TREE INSECTS 49 



If the caterpillars are confined to one or two branches, those branches maj' be 

 removed and the caterpillars destroyed by crushing or burning, or they may be 

 shaken from the branch and destroyed. 



Britton, \V. E., and Friend. R. B. Conn. Agr. Exp. Sta. Bui. 369:274. 1935. 

 Felt, E. P. N. Y. State Mus. Mem. 8(1) :158-162. 1905. 

 McDaniel, E. I. Mich. Agr. Exp. Sta. Spec. Bui. 243:43-44. 1933. 



Elm Leaf Beetle 



CaleniceUa xantJwuieluena Schr. 



The elm leaf beetle, a native of Europe, v\as first found to be destructive in 

 this countrx near Baltimore, Maryland, in 1838, having been introduced a few 

 \cars earlier. At present it is widely distributed across the continent and is the 

 most >erious defoliating insect pest of elm in this countr^^ Elms in urban and 

 suburban situations are principally injured, although occasionally trees in strictly 

 rural localities and in swamps are attacked. The English elm, Camperdown elm, 

 American elm, and Scotch elm seem to be preferred, but all species of elm are 

 subject to attack. Injury is more extensive under certain climatic conditions such 

 as protracted dry spells. 



Several insects prey upon the elm leaf beetle, and a fungus disease attacks the 

 pupal stage causing high mortality, especially during wet weather. 



Description. The newly emerged adults are about 34 inch long and are j^ellow 

 with a dark stripe along each side of the wing covers and a short, dark spot at the 

 base of each wing cover. The upper side of the thorax just behind the head has a 

 dark median spot and one on each side. The beetles which have overwintered 

 are nmch darker in color, being brownish-green. 



The eggs are deposited on the under side of the leaves in clusters of 3 to 26 or 

 more, usually side by side in irregular rows. They are yellow and bottle-shaped, 

 the broader end being attached to the leaf surface. 



The newly hatched larva, or grub, is about 1/20 inch long, the prevailing color 

 is almost black, and the body is covered with tubercles bearing black hairs. 

 As it grows and molts it assumes a yellowish color. The mature grub is about 

 \4 inch long and flatter than the earlier stages. The under side of the body and 

 a broad central stripe on the upper side are bright yellow. A stripe on each side 

 of this central stripe is black as are the head and legs. 



The pupa is bright yellow, broadly oval in shape, and about 1/5 inch long. 

 The body is rounded on top and bears dark hairs on tiny dark tubercles. The 

 adult appendages, held rather close to the body, are plainly discernible. 



Life History. The beetles hibernate in dry, sheltered places such as protected 

 parts of buildings, barns, cracks and crevices in posts and poles, the under side 

 of loose bark, and similar locations. Occasionally they find their way into 

 dwellings where they are sometimes taken for household pests. They are not 

 known, however, to injure any household articles. The beetles emerge from their 

 shelters when the leaves of elm first unfold in the spring and eat in them oval holes 

 about }4 inch in diameter. Soon after mating, the females begin to lay their eggs 

 in small clusters on the under side of the leaves. The eggs hatch in about a week. 

 During early June, the tiny black larvae begin to appear and feed on the lower 

 surface of the leaves, eating all the green tissue and leaving only the veins and the 

 upper leaf surface. It is this type of feeding that is so injurious, the earlier feeding 

 of the adults not being important. In early July the larvae become full grown, 

 crawl down or drop from the tree and transform into bright yellow pupae on the 

 ground at the base of the tree, in near-by cracks and crevices, under loose bark, 



