DISEASES AND OTHER NATURAL ENEMIES 



During the latter part of the caterpillar season one can 

 frequently find dead and dying caterpillars upon the outside of 

 the tent, stretched at full length. Some of these will be simply 

 sluggish, others evidently nearly dead, others dead and ruptur- 

 ing at a touch, letting escape the liquid decomposed body con- 

 tents. Some will be hanging by one end of the body to the 

 tent or twig, as shown in Fig. 9. These caterpillars appear to 

 be affected by one of the bacterial diseases that are known to 

 develop in many insect larvae when they become very abun- 

 dant. The army worm and common cabbage worm are fre- 

 quently destroyed in great numbers by such diseases. While 

 there appeared to be more of these diseased larvae this year 

 than last in southern New Hampshire, the disease was not suffi- 

 ciently destructive to give great hope for the immediate sup- 

 pression of the outbreak. The fact of each colony being 

 somewhat isolated from others will tend to prevent the germs 

 from affecting all the caterpillars of a region. 



After the tent caterpillars are half grown there may be found 

 in many of the nests small dead specimens with the body swol- 

 len and the skin dry and hard. (Fig. 



^ ,v\^^^j^_ V, 10). If these are placed in bottles by 



"'^^^^^^i^^^S ^^■'^'^^^^^^^' ^ fortnight or so later small 



" four-winged flies will emerge from them. 



Fig. lo-Parasitized Cater- These are parasitic ichneumon flies, 

 pillar (Original) j^^^^y i^^^^ developed from eggs placed 



in the young caterpillars by similar parent flies. The eggs 

 hatched into grubs or larvte that developed on the inside of the 

 caterpillars, killing them and absorbing all the bodies except 

 the skin. Within the latter the larvae pupated, to emerge later 

 as flies. We reared many of these parasites, which were 

 kindly determined by Mr. L. O. Howard as Pi'mp/a inquisitor. 

 Comparatively few birds feed upon hairy larvae like the tent 

 caterpillar, but some, like the cuckoos and blue jays, devour 

 them eagerly. The European cuckoo is said to regurgitate the 

 mass of hairy skins swallowed with the caterpillars, and prob- 

 ably our species have the same habit. Many observers have 

 noticed that both the Black-billed and the Yellow-billed Cuckoos 



