182 SHADE-TREES IN TOWNS AND CITIES 



soon as the larvae of these insects hatch they bore their way 

 through the bark into the wood and make a series of gal- 

 leries either immediately beneath the bark or deeper in the 

 tree. In these they develop and emerge as winged insects. 



Leopard Moth {Zeuzera pyrina Fabr.). — The most de- 

 structive species on city trees is the leopard moth. Practi- 

 cally all kinds of shade-trees are attacked by the larva. 

 During the latter days of June and in early July the adult 

 insects are most abundant. The eggs are deposited by the 

 females either singly or in masses, a single adult depositing 

 between five hundred and one thousand eggs. They are 

 usually placed in a bark crevice or other sheltered situation 

 on one of the small twigs or branches. On hatching, the 

 young caterpillar makes its way to the crotch of a small 

 branch or bud and at once bores into the wood tissue. 



It works downward toward the base, and grows very 

 rapidly. Presently it leaves its burrow and wanders to a 

 large branch and again begins feeding. The caterpillars 

 bore a straight channel through the centre of the branch or 

 eat out a large cavity on one side of it. Many of the cater- 

 pillars gnaw an irregular chamber of the size of a man's 

 hand right under the bark. 



Two years are required to complete the life cycle. By 

 the end of the first season the larva is half -grown and has 

 usually made its way to one of the large branches. 



The caterpillars remain in the dormant state during the 

 winter and resume feeding the next spring. During the 

 second summer, growth is rapid, and at the end of the season 

 the larvs reach their full size of two inches or more. In 

 that state they pass the second winter, and early in the 

 spring following work close to the surface and form pupae 

 from which the adult moths emerge. 



