DESTRUCTIVE INSECTS. 173 



moths are ascending the trees, forms a simple, cheap, and 

 very efEective barrier. We have seen such a trap filled with 

 the moths crowding and pushing each other until many of 

 them were killed; in a badly infested orchard we have seen 



at 1 e a s t a thousand 

 moths trying to as- 

 cend a single tree in 

 one evening. 



Tent-caterpillars are 

 serious enemies to ap- 

 ple-trees and some for- 

 est trees in most parts 

 of the country. They 

 have their seasons of 

 increase and decrease. 



Fig. 236.— Apple- tree Tent-caterpillars on 

 their Tent, natural size. 



Fig. 237. —Egg-mass of Tent- 

 caterpillar. 



Some years they nearly strip whole orchards ; and again they 

 diminish in numbers in successive years, till few can be found. 

 The species which usually does the most damage to fruit- 

 trees is shown in Fig. 236, and it is known as the American or 

 Apple-tree Tent-caterpillar {Clisiocampa americana). In the 

 spring, as soon as the leaf-buds of the apple begin to open, 

 the little hairy caterpillars hatch from their varnished egg-ring 

 (Fig. 237), where they have spent the preceding eight or nine 

 months. They feed for five or six weeks and attain the size 



