216 INSECTS 



a host for fleas, may nevertheless be bitten by any of 

 those infesting any of the animals that live with him 

 or in his dwelling places. 



In an ordinarily well-kept house flea larvae cannot 

 develop; but occasionally, when such a house has been 

 kept shut up during a summer, a brood of larvae may 

 develop and become annoying. In such case a free use 

 of gasoline in floor cracks and similar places where the 

 flea larvae live will generally give relief. 



The subject as presented here is a mere outline of 

 what is known and believed; there are other insects 

 that undoubtedly facilitate the spread of disease in man, 

 directly or indirectly, and there are many more that do 

 this for other vertebrate animals. Their importance 

 from this point of view cannot be overestimated, and at 

 the same time it is eloquent testimony that for many 

 ages man and these insects must have dwelt together, to 

 permit so close a union as identity in parasitic affections 

 argues. 



