2 THE CANADIAN ENTOMOLOGIST 



Life-history and Habits of Z. scutellaris, Suflfr. 



On about June 15, the adults are found for the first time in the year feeding 

 on Cottonwood leaves. From then on to the end of the month their numbers 

 increase rapidly. Although these beetles are apparently strong fliers they do 

 not take readily towing, but if disturbed they fall to the ground, feigning death. 

 They are usually present in the largest numbers on the smaller leaved varieties 

 of cottonwoods, and are always more numerous on the lee side of the tree than 

 on the exposed. Trees sheltered by houses also suffer more than others. 



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Fig. 1. 



Cottonwood leaf, upper side, attacked by Z. scutellaris, natural size. 



A. Old feeding punctures of adult. 



B. Blackened blister made by larva. 



C. Epidermis torn awa\' where larva escaped. 



D. Darkened areas over eggs which failed to hatch. 



By June 26, the sexes are mating freely on the leaves, the female browsing 

 peacefully meanwhile. Before the end of the month numerous eggs can be 

 found in the leaves of trees where the beetles have been feeding. These eggs 

 are yellow or green in colour, elliptical, 1 mm long by 5 mm wide. They are 

 laid in a small cavity close to the upper epidermis of the leaf. This is con- 

 nected to a hole on the underside of the leaf by a short diagonal tunnel. 



Soon after the egg has been laid the tissues above the cavity turn brown, 

 thus the location of each egg is marked on the upper side of the leaf by a small 

 brown spot about 1 mm in diameter (Fig. 1, D). 



From the egg hatches a small, flat larva with a broad head, flattened dorso- 



