124 



THE FOREST TENT CATERPILLAR 



lis after the cocoons are spun. The method of egg-laying is 



shown in Fig. 51. The eggs hatch into minute grubs that 



develop at the expense of the 

 chyrsalis,finally eating up near- 

 ly all their substance. About 

 two weeks from the time the 

 eggs are laid the parasitic lar- 

 vae change to pupse, and very 

 soon afterwards again change 

 to adults. 



Two other small parasites 

 of the Chalcid family were 

 also reared, although they 

 were not at all abundant. One 

 of these was the species, called 

 by entomologists Diglochia 

 omnivorus, while the other has 

 not been determined. We 



have also reared one species of parasite from the eggs of the 



Forest Tent Caterpillars. 



Fig. 51. — Ichneumon fly depositing an 

 egg within cocoon. (Slightly magnified.) 



BACTERIAL DISEASES 



It is a well-known fact that seasons of dry weather are favora- 

 ble to the development of insects injurious to plant life. This 

 is especially true of caterpillars, and so the extraordinary dry- 

 ness of the spring and summer of 1899 was very favorable to 

 the increase of the Forest Tent Caterpillars. Their various 

 bird and insect enemies did good service in destroying them, 

 but the bacterial diseases that are likely to affect such insects 

 during wet seasons did them little harm. The recent outbreak 

 of the common American Tent Caterpillar was brought to an 

 end two years ago chiefly through the agency of such a dis- 

 ease, the wet weather being favorable to it. 



These bacterial, and fungus diseases have been present, to 

 a limited extent, among these caterpillars, both last year and 

 the year before. Should next June be a very wet month, 

 these diseases would probably do much to check the outbreak. 



