40 THE HOUSE FLY 



season. Flies are often seen crawling about on window panes 

 in a sluggish manner, and, if caught and microscopically 

 examined, will frequently be noticed to be infected by this 

 fly-killing fungus, the spores of which destroy them. 



Flies are the hosts of a variety of external and internal 

 parasites, but these, as a rule, only tend to somewhat 

 deplete the vital forces of the fly, and are not of much 

 practical account in the destruction of these pests. 



The spider is another natural enemy of the House Fly, 

 but it is of little practical value as an ally to us in the war 

 of extermination against the House Fly which enlightened 

 communities of men are undertaking. 



If we allowed the House Spider to spin his webs without 

 interference in our dwellings, a considerable number of 

 flies would be done to death, but no tidy housewife would 

 tolerate spiders' webs in her home. However, there is no 

 excuse for destroying spiders and their webs in our gardens, 

 except under exceptional circumstances. 



There are many kinds of ground spiders which do not 

 spin webs, but which, nevertheless, prey largely on flies by 

 springing upon them from lurking places. Spiders are 

 carnivorous, and prey upon a variety of insects which are 

 harmful to man, and they, in consequence, should be re- 

 garded as valuable allies. 



The eggs, maggots, and chrysalides of flies are devoured 

 wholesale by an army of enemies such, for instance, as 

 carnivorous beetles, centipedes, and ants. 



There are certain kinds of flies which are very tiny. 

 These little creatures are active agents in keeping House 

 Flies in check. They are ever on the alert to find fly maggots 

 or the chrysalides, in which they deposit an egg. This egg 



