144 



feel considerable confideuce that this disease may readily be transferred 

 from place to place. 



As to the possibility of preserving the germs from year to year, Pro- 

 fessor Forbes has succeeded in one instance in carrying a species of 

 micrococcus in culture- tubes over winter, inoculating with these tlie fol- 

 lowing summer and producing apparently the specific disease of that 

 organism. We may consider, then, leaving out of the question the 

 difficulties of the process, that it is possible to both hold the germs for 

 a limited time and to start the disease anew in the same or another 

 locality. 



Admitting, however, the possibility of jireserving and transporting 

 the disease, we have still the problem of how to make the disease spread 

 with that certainty and rapidity necessary to make it of practical value. 

 Moreover, any remedy to be of general utility must be of such a nature 

 as to be easily and properly applied by people unacquainted with the 

 methods of germ culture. It might be quite impracticable to send a 

 trained bacteriologist into every county in a State to inoculate the 

 chinch bug with flacherie. 



The slowness with which the disease operates, even at best, makes 

 it doubtful whether the method can ever be used where immediate re- 

 sults are desired. This is particularly true of all but the bacterial 

 forms, and even with these a ijeriod of incubation must ela[»se after the 

 first introduction, and a further period before the disease will spread 

 from those first infected to other individuals. We can scarcely look 

 to it, therefore, as a source of relief from sudden and unexpected in- 

 vasions of insects. When successfully introduced its spread will de- 

 pend upon a number of variable conditions, abundance of material upon 

 which to feed, amount of communication among insects, atmospheric 

 conditions, etc., so that final results would be uncertain. The applica- 

 tion of such diseases may, therefore, be considered as limited to the 

 power of preserving temporarily and introducing into different local- 

 ities, and not embracing the power to regulate the conditions which 

 control the spread of the disease once introduced. 



Naturally such diseases spread most rapidly among gregarious in- 

 sects and least rapidly among solitary species, and of solitary species 

 most rapidly among those most numerous in individuals and least rap- 

 idly among those that are rare. The remedy, therefore, will be limited 

 in general to wide spread gregarious insects or those occurring con- 

 stantly or periodically in great numbers. Of these we may mention as 

 examples the tent caterpillars, web-worms, cabbage-worms, chinch- 

 bugs, locusts. May beetles, army worms, etc. 



The final test will, of course, be the cost as compared with other rem- 

 edies equally effective. But cost will depend almost entirely upon the 

 time in which the results are desired. In a cabbage-patch the disease 

 could be introduced in a single spot at slight cost, and in time it might 

 spread over the entire patch. Or, if introduced so as to cover the en- 



