306 ILLINOIS ACADEMY OF SCIENCE 



The effectiveness of entomogenous fungi in both nat- 

 ural and artificially induced epidemics, appears to de- 

 pend very largely upon climatic conditions. Indeed, 

 those students of the subject who are most pessimistic 

 concerning the practical utility of fungus diseases in in- 

 secticidal operations, recognize their great effectiveness 

 under favorable weather conditions, but hold that suffi- 

 ciently favorable conditions to insure success are en- 

 countered too rarely to justify the enthusiasm for the 

 method which some of its advocates have expressed. 



The procedure followed by former students of the sub- 

 ject has usually been to propagate some species of fun- 

 gus diseased on artificial media, and to distribute the 

 spores produced or the resulting culture of the organism, 

 in fields or in other situations where the insect pest 

 against which the operation was directed happened to be 

 abundant. In such a case the results of the test and the 

 conclusions of the operator are determined by the 

 weather conditions which chance to prevail at the time. 

 Laboratory studies generally have been little more than 

 field tests in miniature, and usually with as little atten- 

 tion given to the precise relation between the results ob- 

 tained and the conditions governing the test. 



In organizing the present series of studies it was pro- 

 posed to analyze the problem thoroughly and to study its 

 various elements one by one : to proceed under carefully 

 controlled conditions, and by changing certain of these 

 conditions one at a time, to find how various degrees of 

 temperatures, various percentages of humidity, and va- 

 rious other fators may influence the germination of the 

 spores and the power of the fungus to penetrate the body 

 of its insect host; to find how cultivation of the fungus 

 on artificial media may influence its virulence or power 

 to attack its proper insect host ; to find how temperature, 

 humidity and other factors may influence the power of the 

 insect to resist infection when exposed to contamination 

 with a fungus disease : and finally, in the light of the data 

 thus accumualted, to canvass the meteorological records 

 and to determine if practicable in what habitats of what 

 localities during what months or seasons, fungus diseases 



