944 MICROBIAL DISEASES OF INSECTS 



about an apiary, winds, hives which have housed infected colonies, 

 combs from such colonies, or bees dead of the disease unless they serve 

 to contaminate the water supply. Thus these latter mentioned im- 

 probabilities can be eliminated when dealing with control measures. 



MISCELLANEOUS INSECT DISEASES 

 ENTOMOPHTHORACE^E* 



ENTOMOGENOUS FUNGI. * Empusa muscce is the best known mem- 

 ber of this group of insect parasites. This species attacks the house 

 fly. The fly weakened by the disease fastens itself to the wall or win- 

 dow pane by its mouth parts. The mold fruiting upon the dead body 

 discharges its spore masses which adhere where they strike. Such 

 dead flies are frequently surrounded by a discolored circle where great 

 numbers of these spores are fixed upon the wall. Natural epidemics 

 of this kind frequently destroy flies and other insects but attempts to 

 produce such epidemics by inoculation have generally failed because 

 the fungus is too greatly dependent upon uncontrollable factors of 

 temperature and humidity. 



Other entomogenous fungi include representatives of many different 

 groups. The life histories of some of them are well-known but many 

 of them have been only partially studied. The practical usefulness 

 of some of these species, notably Sporotrichum glob^iliferum, as a chinch- 

 bug disease, has been studied carefully. While the work was markedly 

 successful in causing an epidemic disease when conditions favored it, 

 dependence upon particular conditions was so complete that the 

 production of the disease as an effective destroyer of pests failed. 

 Similar results have attended the effort to use other fungi as insect- 

 destroyers. The conditions which make possible their development in 

 epidemic form only occur occasionally. These conditions in themselves 

 are, as a rule, very unfavorable to insects. Under other climatic con- 

 ditions, these diseases appear only as isolated cases, negligible in their 

 effect upon the insect population, no matter how carefully the inoculat- 

 ing material is spread by man. 



One great series of fungi the Laboulbeniales is limited to insect 

 parasitism. The genera and species of this group are very specialized 



* Prepared by Charles Thorn. 



