308 ILLINOIS ACADEMY OF SCIENCE 



dusted with the dry spores, while an emulsion of the 

 spores in sterile physiological salt solution was prepared, 

 and injected by means of a hpodermic syringe into the 

 sub-hypodermal tissues of the pupae in the second series, 

 each pupa in the inoculated series receiving many times 

 the minimum fatal number of spores. That this method 

 of inoculating the pupae is not injurious mechanically, is 

 conclusively demonstrated by the fact that other pupae 

 receiving injections of sterile physiological salt solution, 

 similarly administered but several times greater in vol- 

 ume, survived the experience apparently uninjured and 

 developed into normal adults. 



The case history of this disease in the cecropia pupa 

 presents several rather sharply defined stages which af- 

 ford an excellent index to the effect of any combination 

 of temperature and humidity conditions. The stages may 

 be outlined briefly as follows: (1) The spores must 

 germinate and penetrate the body wall of the pupa in 

 sufficient numbers to overcome the natural resistance of 

 the insect. This conquest of the host animal by the dis- 

 ease, and the development of the fungus at the expense 

 of its tissues may be recognized by the characteristic 

 hardening of the body of the insect commonly called 

 mummification, and the two series of pupae just de- 

 scribed afford an accurate check at this point, on those 

 conditions which either entirely prevent the germination 

 of the spores in contact with the pupa, or prevent their 

 penetration of the body wall of the insect in numbers 

 sufficient to infect the animal. (2) Having completed 

 its development within the body of its host, the fungus 

 must again penetrate the body wall to reach the exterior 

 where the new crop of spores may be produced in a po- 

 sition most favorable for dissemination. This stage is 

 characterized by the appearance of velvety-white masses 

 of hyphae which appear first thrpugh the thinner por- 

 tions of the integument between the abdominal segments, 

 but which eventually may cover the entire surface. (3) 

 The first evidence of spore formation consists of the 

 appearance upon the velvety-white masses of aerial 

 hyphae of small, irregular, light olive-green patches, 



