208 BOARD OF AGRICULTURE. 



this pest 0/f our orchards and shade trees. The canker-worm 

 is attacked by other parasites, and great numbers are eaten 

 by caruiverous insects as well as by birds and other animals ; 

 but our little egg-parasite is undoubtedly their most destruct- 

 ive enemy. Knowing tile habits of these enemies of the can- 

 ker-worm, we can readily understand the sudden diminution 

 and increase in its numbers during a series of years. It may 

 be well to state in connection with this that they never wholly 

 disappear ; for, any year, a careful search will reveal a few at 

 least on almost every tree which they are in the habit of in 

 festing. These few are so scattered they are not easily found 

 by parasites and other enemies, and hence these enemies di- 

 minish very rapidly in numbers, till finally a series of years 

 happen to be favorable for the increase of the canker-worm 

 and they multiply enormously and entirely out of proportion 

 to the numbers of the parasites. Soon the canker-worms 

 overstock the trees they inhabit and their very abundance gives 

 plenty of food for the parasites, which increase so rapidly in 

 consequence as to overcome them in a very few years. I know 

 the disappearance of the canker-worm is frequently ascribed 

 to other causes. Their last disappearance in the region of 

 New Haven, was ascribed by many to the introduction of the 

 English sparrow. Watching them in the last year of their 

 abundance, however, it was quite evident that tlie sparrows 

 were not the most efficient of their enemies. It was not 

 iincommon to see one of our little parasitic flies close to a 

 female canker worm, while she was depositing her eggs, and 

 puncturing every one of them while still freshly laid and soft. 

 Sometimes several were at work on the same cluster of eggs, 

 contending for the opportunity of depositing their eggs. Other 

 enemies of the canker-worm increased in similar proportions. 

 In the spring and early summer, both while the females were 

 going up the trees to deposit their eggs, and afterward while 

 the worms were coming down, a big metallic green beetle, 

 which in ordinary seasons is very scarce and seldom seen, ap- 

 peared in great abundance, a dozen being frequently found 

 about a single tree, devouring the helpless females or worms 

 as they came along. With such an army of insect destroyers 



