3U JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 5 



litis, especially as they have been found abundant in certain maritime 

 districts where epidemic poliomyelitis has occurred. The seasonal 

 distribution of these flies is not exactly like that of Stomoxys, since 

 the horse flies do not have such brief life cycles and their greatest 

 abundance is rather in midsummer than in the early fall. If both 

 should prove to be associated with poliomyelitis, then there is perhaps 

 good evidence that neither Stomoxys nor Tabanus is a specific carrier, 

 as the two are quite different insects and it would be very unlikely for 

 the same parasite to affect' both. 



Another group, the Simuliidse, includes small biting flies which 

 sometimes appear in enormous numbers in certain localities, particu- 

 larly in the spring of the year. In Europe one of these, SimuUum 

 reptans has been thought to transmit pellagra, but this suspicion has 

 not yet been proved, and American investigators are inclined greatly 

 to doubt it. The larvae of these flies breed exclusively in swiftly 

 running brooks, and the adults are on the wing mainly in the spring 

 of the year, so that their association with anterior poliomyelitis would 

 be very improbable, as poliomyelitis is not confined to such localities 

 and its greatest seasonal incidence does not correspond with the seasonal 

 abundance of these insects. 



Among the midges, another extensive family of small flies, (Chiron- 

 omidse), which are generally innocuous, are a few species which suck 

 blood. These are quite vicious biters and might perhaps be asso- 

 ciated with the spread of poliomyelitis, although we have not been 

 able to demonstrate their presence in the vicinity of many cases. 

 Also, these flies are very small and rarely, if ever, bite animals, so that 

 any infection from animals could not ordinarily be due to them. They 

 thus appear to be much less likely than mosquitoes as carriers of 

 poliomyelitis, aside from the fact that they have never yet been asso- 

 ciated with any disease. 



Somewhat similar small flies belonging to still another family, the 

 Psychodidse, are blood-sucking in habits. These are included in the 

 genus Phlehotonius and its allies, but they occur rarely, if at all. in our 

 region, and need not be considered in the present connection. 



The Siphonaptera, a group of small wingless epizoic parasites known 

 as fleas, have been associated as casual carriers of bubonic plague and 

 are known to be the most common agents in the transfer of this disease. 

 They have been suggested by Conn ^ as the possible carriers of acute 

 epidemic poliomyelitis, but their habits and seasonal distribution 

 appear in no way to bear out such a supposition. Their relative 

 abundance in summer and winter does not coincide with ths incidence 



1 Rept. State Bd. Health, Connecticut, 1910-11 (1912). 



