LIFE OF JAMES DWIGHT DANA 



some females coming out of the ground and climbing the 

 trees even when the ground is frozen, and many when- 

 ever there is a thaw. In the spring, the females are again 

 numerous, though far less so than in November. 



" The male of the insect is a grayish-winged miller, 

 about two-thirds of an inch in length, and much like an 

 ordinary moth in general form. The female is a little 

 shorter and much stouter than the male, and without 

 wings. Being thus wingless, they have to crawl up the 

 trees in order to lay their eggs upon its branches. In 

 the proper season the females may be seen on their march 

 up the trunk, though so like the bark in color as to re- 

 quire some little attention to find them. The males at 

 the same time, especially just at dark, are flitting about 

 near the trees in great numbers. Some of the females 

 blunderingly ascend posts and fences and the sides of 

 houses, and in such places lay their patches of eggs. But 

 in general, they succeed in finding the trunk of a tree, 

 and especially their favorite, the elm ; and when once on 

 the ascent, they continue upward until they have reached 

 the extremities of the branches, or else until the laying 

 time, which usually comes from a few hours to a few days 

 after the ascent is commenced. The eggs are thus dis- 

 tributed everywhere over the tree, from the lower part of 

 the trunk to the top. They are consequently placed for 

 the most part where the young as soon as hatched (in 

 May) will find food near at hand. The eggs laid on the 

 fences and sides of houses hatch like others, but the 

 young from these generally die for want of food. 



' The young from the eggs are the canker-worms, and 

 the canker-worm is hence the young state of a miller, 

 just as the caterpillar is the young of an ordinary butterfly. 

 These worms when they leave the trees in June (generally 

 before or by the loth) bury themselves in the ground, 

 where each becomes a chrysalis, and in this state they 

 remain, without locomotion or feeding, until ready to 

 emerge as perfect insects in October and the following 

 months. A single female lays on an average 75 eggs, 

 and if each canker-worm in a season eats 10 leaves the 

 brood of one single female may consume 750 leaves. 



Now the fact that the females are wingless renders 

 the troughs of oil around the tree a sure means of de- 

 stroying them ; for the slightest besmearing of the body 



360 



