REPORT OF THE ENTOMOLOGIST. 529 



and possessed vigor enough to transform into pupse; later the fungus 

 grew, and pressing the chitinous portion of the pupa apart, forced 

 itself to the air to fructify. 



Plants not usuall}^ eaten by the caterpillars, as well as others not 

 eaten at all, have upon them the largest numbers of caterpillars 

 killed by the fungus, provided that they grew in the vicinity of 

 suitable food-plants. Perhaps unsuitable food, predisposing the 

 caterrjillars for any disease, is one of the causes of the innumerable 

 host Ivilled by this fungus. 



The white cocoons of a parasite {Apanteles Jiyphantrice) were in 

 some cases observed to be covered with similar fungus spores. Open- 

 ing such cocoons it was seen that the spores were not simply blown 

 upon the silk and there retained, but that they came from the victim 

 within, and had forced their way through the very dense silken mass. 



EXPERIMENTS TO OBTAIN PERCENTAGE OP DISEASED CATERPILLARS. 



Experiment I : 



One hundred and twenty-five nearly grown caterpillars were 

 gathered (October 7, 1886) at random in one of our public 

 parks. They were imprisoned in large glass jars, and daily 

 supplied with suitable food. 

 Result, October 18, 1886: 

 11 apparently healthy pupae. 

 3 deformed pupae. 

 18 yellow cocoons of Meteorus hyphantrice. 

 9 dead pupae, killed by fungus or otherwise. 

 84 dead caterpillars, killed by fungus or otherwise. 



125 

 In the earth of the jar were found 17 pupae of Tachina flies, leav- 

 ing 67 caterpillars and 9 pupae killed by the fungus, or 61 per cent. 



Experiment II: 



One hundred and twenty-five nearly grown caterpillars were 

 gathered (October 7, 1886) from a trunk of a soft maple 

 (unsuitable food) and treated as above. 

 Result, October 18, 1886: 

 8 apparently healthy pupae. 



1 detormed pupa. 



7 yellow cocoons of Meteorus hyphantrice. 

 3 dead pupae, killed by fungus or otherwise. 

 104 dead caterpillars, killed by fungus or otherwise. 



2 cocoons containing Tachina larvae. 



125 



In the earth of the jar were found 28 pupae of Tachina "flies, leav- 

 ing 76 caterpillars and 3 pupas killed by fungus, or 63 per cent. 



In both experiments it has been assumed that each Tachina fly had 

 killed one caterpillar. 



On November 15, 1886, the jars were again investigated and it was 

 found that a number of the_ pupae had been killed by the fungus since 

 October 18, 1886, and that in fact all the remaining ones appeared 

 diseased. The percentage of death by the fungus in the two experi- 

 ments was thus increased to 63 per cent, in Experiment I and to 67 

 per cent in Experiment II. 



34 AG— '86 



