152 INSECTS 



very narrow limits only, and succumb readily to vari- 

 ations beyond the normal range. 



We have seen also that, not only dp insects suffer 

 from germ diseases, but that these ofteft assume the 

 dimensions of epidemics and form a very important 

 factor in nature's scheme of insect control; a factor of 

 which we have not yet made the utmost possible use 

 in our dealing with the economically important species. 



