OUR FRIENDS AND FOES 



161 



the house, it will be advisable to inquire into the condi- 

 tions of the stables in the vicinity. Properly kept 

 stables will greatly reduce the number of flies. 



It will be found that gregarious insects do not appear 

 in such great numbers year after year: there must be 

 some cause for this. It will be an interesting problem 

 to be solved. 



The enemies of insects increase as well as the com- 

 petitors. Parasites, attracted by innumerable insects 

 upon which they prey, increase so rapidly as to devour 

 their own means of support. They in turn succumb 

 and the defeated host rallies ; so the alternate warfare 

 goes on forever. And in the activities of these beings 

 which we are wont to consider beneath us, there is 

 much for profitable observation and careful study. 



