601 



importance is that of the adults coming to water to drink. Portschinsky 1 has found 

 that by applying kerosene to the pool they frequent the adults are killed, and 

 Hine 2 that the same oil kills the larvas that fall into the water from eggs laid on 

 plants above. 



\Tabanidfp are not only of importance as purely biting insects, for they may 

 often convey pathogenic organisms from one animal to another, such as the 

 bacillus of anthrax, which they are known to carry, and possibly also trypano- 

 somes in regard to man. Chrysops also acts as a host of Filaria loa in South 

 Nigeria (Leiper, Brit. Med. Journ., January, 1912, pp. 39-40). Two species are 

 incriminated, viz., C. silacea and C. dimidiata. With animals these flies play 

 a more important part, for MM. Sergent, in Algeria, have proved that species of 

 Tabanus are able to transmit three forms of animal trypanosomes by biting a 

 healthy animal as long as twenty-two hours after having bitten an unhealthy 



FIG. 415. The ox gad fly (Tabanus bovinus, Linn.). 



one. In India they have also been shown to transmit the parasite of "surra" 

 in dogs and rabbits by Rogers. Other observers have since corroborated these 

 results, and Mitzmain, who has recently performed valuable work in this connection, 

 states that T. striatus is undoubtedly the carrier of this disease in the Philippine 

 Islands. Certain members of the genus Haematopota have also been shown to be 

 capable of the direct transmission of Trypanosoma evansi. Martoglio (Ann. 

 d'lg. sper., 1913, xxiii, N.S., No. 3, pp. 363-366) states that the trypanosome disease 

 of dromedaries known as salaf is transmitted by Tabamdce, especially Pangonia 

 (P. magretti and P. beckeri) in Italian Somaliland. It is quite likely that these 

 flies play a much greater part in the spread of such diseases than is imagined 

 at the present time. 



[The Tabanidcc are divided into two groups or subfamilies : (i) The 



1 Vide Bull. 20, N. Sc., U.S. Div. Ent. 



- " Tabanidce of Ohio," Ohio State University Bull. 19, 1903, sec. 7, p. 14. 



