Courtesy Can. For. Serv., Can. Dep. Environ., 
Sault Ste. Marie, Ont. 
Figure 113.—The imported willow leaf beetle, 
Plagiodera versicolora. Note skeletonization of leaves 
by larvae. 
The winter is spent in the adult stage under the bark, or in debris or tufts of grass 
around or near the base of trees. The beetles emerge in April or May and feed for a 
short period by skeletonizing the leaves or by cutting holes through them. Then the 
female lays irregular masses of eggs on the leaves. Hatching occurs in about a 
week. The larvae are gregarious and feed in groups or in rows on the leaf surfaces, 
which they skeletonize. Three generations per year, and a partial fourth, have been 
recorded in Massachusetts. Additional generations probably occur farther south- 
ward. Heavily infested trees may become entirely brown as early as mid-June. A 
considerable degree of natural control is exerted by the imported pupal parasite, 
Schizonotus latus (Walker) (326). Extremely cold winters are also fatal to poorly 
protected adults. 
Systena marginalis (liliger) feeds on oak in the Midwest and on baldcypress in 
northern Florida and southern Georgia. The adult is dull, pale yellow except for two 
black lines along the front margin of the elytra and a single black line along the hind 
margin. The wing covers are densely and coarsely punctate. Adults are present from 
mid-June to late August and feed by gouging out linear-shaped punctures in the 
leaves. This usually causes part or all of a baldcypress leaflet to turn red and die. 
The beetles occur in large swarms that tend to move about, spending only | to 3 
days in any one place. A single swarm may encompass more than a dozen trees. 
Zengophora scutellaris Suffrian, an introduced species, feeds on cottonwood 
and other poplars from New York and New Jersey to Montana and New Mexico. 
The adult is about 4 mm long. The head, prothorax, and legs are yellow; the tarsal 
claws are toothed; there is a prominent tubercle on each side of the prothorax; the 
elytra are coarsely punctate; and the abdomen is black. The remainder of the body 
is yellow. Adults feed by skeletonizing the lower surfaces of leaves. The larvae feed 
singly in the soft inner tissues, chiefly against the upper surface of the leaf, making 
265 
