13 



season for the ravages of the chinch bug draws near, there is often a 

 radical reduction instead of an increase in numbers. The forecasting 

 of chinch-bug outbreaks is therefore based wholly upon the fore- 

 casting, months in advance, of meteorological conditions that are 

 likely to occur at certain periods. If the farmer would but watch 

 the seasons, he need not be taken unawares by chinch-bug outbreaks, 

 as dry weather during the two breeding seasons is usually sufficient 

 to precipitate an invasion the following year, provided that, at the 

 critical period or time of hatching, rains do not destroy the young. 

 The general statement may be made that throughout the Middle 

 West a dry June followed by a dry August is favorable for the develop- 

 ment of chinch bugs. These dates will of course vary, and must not 

 be applied to the more southern or more northern localities. 



PARASITIC FUNGI. 



The fact that the abundance and consequent influence of fungous 

 enemies of the chinch bug are almost entirely dependent upon 

 meteorological conditions is sufficient to place them in a secondary 

 position, even though they ma}^, under favorable weather conditions, 

 act as natural checks. 



Dr. Henry Shimer "• long ago made the truthful and important 

 statement that 'Hhis disease among the chinch bugs was associated 

 with the long-continued wet, cloudy, cool weather that prevailed 

 during a greater portion of the period of their development." These 

 are precisely the conditions under which these fungi have been 

 observed to prove the most fatal to the chinch bug during recent 

 years where their introduction among the host insects was accom- 

 plished by artificial means. Although Shimer probably never 

 anticipated the artificial cultivation of his '^ disease" and the results 

 which have since been obtained from its artificial dissemination in 

 the fields, yet his careful and painstaking studies must ever be asso- 

 ciated with the application of fungous diseases in the destruction 

 of insects in America. 



The principal fungus to be artificially employed in destroj^ing 

 chinch bugs has come to be known as the chinch-bug fungus {Sporo- 

 trichum glohuliferum Speg.), and this is the one used by Doctor Snow 

 in Kansas for artificial introduction into localities where there is an 

 overabundance of these bugs. 



Doctors Roland Thaxter and S. A. Forbes devised a method of 

 artificial cultivation, the latter using a basis of sterilized mixture of 

 beef broth and corn meal. As this fungus has many other host 

 insects, it is probably present to a greater or less degree throughout 

 the country every year. There is no doubt that during wet weather 



a Proc. Acad. Nat. Sci. Phila., May, 1867. 

 [Cir. li;i] 



