February, '13] BRUES: STABLE FLY AND INFANTILE PARALYSIS 105 



examination or by questions relative to the history of the case before 

 the onset of symptoms. Certain Reduviid bugs are know to carry a 

 trypanosome disease of man known as barbiero fever in the American 

 tropics, but as all of our native species of this family appear to inflict 

 very painful bites, the failure to obtain histories of such bites, seemed 

 to eliminate these bugs from any connection with poliomyelitis. 



There remain various Diptera with blood-sucking habits, and some 

 of these seemed to offer the most promising field for investigation. 

 Many, however, for one reason or another fail to meet all necessary 

 requirements. Gadflies, of the genus Tabanus have been sometimes 

 especially noticeable in localities where epidemics of poliomyelitis 

 have occurred, notably in maritime towns, but they are not so abun- 

 dant in the inland rural communities. Their place is there taken by 

 the related Chrysops, but these do not occur in the later part of summer, 

 when the disease shows its greatest incidence. On account of their 

 great thirst for blood, the small black flies of the genus Simulium have 

 been suspected as carriers of a human disease known as pellagra. They 

 are most abundant in the spring, at least in our region, and may 

 thus be ruled out as possible vectors for the virus of poliomyelitis. 

 The horn-fly, Hoematohia, appears in abundance occasionally upon 

 animals on farms, but was seen in the vicinity of only a small pro- 

 portion of the cases visited. 



In addition to the insects already mentioned, which might be ex- 

 pected to act as specific carriers, there are others, like the common 

 house fly which may act as contaminative carriers for certain bacterial 

 diseases. Such a method of spread is always supplementary to in- 

 fection by contact, ingestion, etc., and as such channels of infection 

 had not been demonstrated otherwise, it seemed very unlikely that the 

 house fly should bear any relation to the transmission of poliomyelitis. 



After thus considering the various possibilities, it appeared probable 

 that the common blood-sucking stable fly, Stotnoxys calcitrans, might 

 be implicated. In fact, this seemed to be the only insect which could 

 not be disregarded for one or more of the reasons set forth above. 

 Briefly, the reasons for suspecting a relation between Stomoxys and 

 poliomyelitis were the following: 



1. The blood-sucking habits of the adult fly suit it for the transfer 

 of virus present in the blood. 



2. The seasonal abundance of the fly is very closely correlated with 

 the incidence of the disease, rising rapidly during the summer, and 

 reaching a maximum in July and August; then slowly declining in 

 September and October. 



3. The geographical distribution of the fly is, so far as can be ascer^ 

 tained, wider, or at least co-extensive with that of poliomyelitis. 



