THE "WILT DISEASE," OR "FLACHERIE," OF 

 THE GYPSY MOTH. 1 



I. Caterpillar Diseases in General. 



The production of diseases is one of nature's methods of 

 quickly checking the overproduction of living things. Animals, 

 including man, and plants all have their own specific infec- 

 tious diseases, which usually appear whenever a species be- 

 comes so numerous that it menaces the prosperity of the 

 coming generations. In the animal kingdom the possibility 

 of overproduction is especially apt to occur in insects, since 

 they form by far the largest portion of the world's fauna, 

 and have a high rate of reproductivity. Insects, small though 

 they are individually, form in their totality an immense mass 

 of living matter. Of this mass we can get only a slight con- 

 ception, even when we consider that insects are everywhere 

 present, not only as a few scattered individuals, but in such 

 enormous numbers that they constitute, as it were, a world in 

 themselves. "We may say without hesitation that among all the 

 conditions which arise from and are caused by animals, there 

 is none more widely distributed, more many-sided and which 

 interferes more deeply with life on our planet than that which 

 is brought about by insects. As Graber says : 



Man may unwisely neglect these creatures as he does many things ; 

 but their power for evil crushes him the more; indeed, it may destroy 

 him if he persists in his neglect. 



Now, such a power may be checked by nature by one of the 

 most efficient means which she possesses, the infectious 

 diseases. 



Owing to the profound influence which insects exert upon us 

 and our culture, attention has been drawn to their diseases. 

 A close study has been made of some of these; especially -of 



1 Contributions of the Entomological Laboratory of the Bussey Institution, Harvard Uni- 

 versity, No. 36. 



