INSECTS AND ENTOMOLOGISTS 



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find a suitable medium to propagate, and where they may or may 

 not be in position to get into the proper portion of the human animal. 

 Almost any sort of insect may be a carrier, although there are some 

 few peculiarly adapted for the purpose, and such a carrier may be 

 the transmitting agent for a variety of diseases : it is not itself affected 

 by any, and is in no sense a fellow sufferer. 



It is different in the case of intermediate hosts ; here the insect itself 

 harbors one stage of the morbific organism and is itself a sufferer from 

 one form of the disease. Its power of transmission is strictly limited 

 and is restricted to one disease alone. 



The best known and most abundant of the germ carriers is the 

 common house-fly more recently called " typhoid fly." Now it un- 



FlG. 4. 



The house-fly, with its larva and details of structure ; after Howard, U. S. 

 Department of Agriculture. 



doubtedly is a typhoid fly, but it is only one of several species that may 

 be equally effective, and it is by no means a carrier of typhoid germs 

 only. Its habits are such that it may be a transmitting agent for any 

 intestinal disease and for many of the pulmonary and bronchial troubles 

 as well. In a typhus or cholera epidemic it is a " cholera " or " typhus 

 fly " and to call it the " typhoid fly " gives an unfounded suggestion 

 of definite relationship between disease and insect. 



But it certainly is marvelously well adapted as a carrying agent. Its 

 omnivorous feeding habits, its persistence in seeking entrance at places 

 where savory or other pungent odors attract it, and its foot and mouth 

 structure make a combination difficult to equal. The pulvilli of the 

 feet with their numerous minute hooked hairs are ideal collectors of 

 microorganisms, and the lobed, lip-like mouth structure, with its array 

 of pseudo-trachea for surface scraping, can hardly be surpassed in 

 effectiveness. No doubt the house-fly is a danger of the first order, 

 and there is no economic problem now before the sanitarian, of more 

 importance than the elimination of this pest. That it can be done 

 there is no doubt, and that in time it will be clone is equally certain. 



