474 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 7 



(2) Can we introduce it into the infested locality where it is not 

 known to occur? 



(3) Will the fungus establish itself and will it spread and become 

 effective? 



On the whole, a favorable answer can be given to the first two ques- 

 tions. Many of the parasitic fungi have been cultivated on artificial 

 media or on living insects kept in confinement. Such fungi have been 

 introduced among healthy insects when the occasion warranted such 

 procedure. The third question, however, has offered difficulties which 

 in most cases have been insurmountable. Fungi are very dependent 

 upon external conditions and in many cases the apparent absence of a 

 particular fungus in a locality is usually an index of conditions unfavor- 

 able for its development, and an artificial introduction will be useless. 

 If a fungus does establish itself in a locality it may not spread far 

 from the centers of artificial infection, showing that conditions are 

 favorable in and near the centers of infection, but not beyond them. 

 A certain amount of success has been achieved in one case and I will 

 give an account of this after having presented some of the difficulties 

 which were encountered by competent investigators who showed 

 that in general the economic value of certain fungi has been over- 

 estimated. 



In 1892, Franz Tangl, at one time interested in this subject, and 

 now a well known physiologist at the University of Budapest, per- 

 formed some infection experiments on nun moth caterpillars by using 

 spore emulsions of Botrytis hassiana. In the laboratory the experi- 

 ments succeeded' since all of the infected caterpillars died of "mus- 

 cardine. " Infection experiments in nature, however, where infested 

 trees were thoroughly sprayed with spore emulsions, gave negative 

 results. The nun moth caterpillars flourished as before. V. Tubeuf, 

 who has done a great deal of work on caterpillar diseases, tried a series 

 of similar experiments, and likewise obtained negative results when he 

 tried to infect caterpillars in nature with Cordyceps militaris. 



Recently Billings and Glenn (1911) in attempting the artificial use 

 of Sporotrichum globuliferum, the etiological factor of the white fungus 

 disease of chinch bugs in Kansas, have reached very similar conclusions. 

 In a summary of their experiments, they saj^: 



(1) "In fields where the natural presence of the fungus is plainly 

 evident, its effect on the bugs cannot be accelerated to any appreciable 

 degree by the artificial introduction of spores. 



(2) "In fields where the fungus is not in evidence spores introduced 

 artificially have no measurable effect. 



(3) "Apparent absence of the fungus among chinch bugs in a field 

 is evidence of unfavorable conditions rather than lack of fungous spores. 



