ROLE OF STOMOXYS CALCITRANS. 477 



certainly the carrier of surra and that the mortality is greatest during 

 the months when this fly is most prevalent. 



Daruty(i6) says that in Mauritius Stomoxys nigra plays the same part 

 in the spread of surra as the tsetse fly does in Africa in the spread of nagana. 



Diexonne<i'') notes the fact that a surra epizootic broke out in Mauri- 

 tius simultaneously with the appearance of Stomoxys. 



Laveran and Mesnil(i8) mention Stomoxys as a probable transmitter 

 of surra. 



Mohler and Thompson (i9) state that in the outbreak of surra among the 

 imported cattle landed on an island near New York, Stomoxys calcitrans 

 probably was not a factor in the spread of the infection. A species of 

 Tabanus was incriminated. 



Darling, (20) jn discussing the mode of transmission of Tr. hippicum,, 

 the agent of murrina, believes that it is extremely unlikely that Stomoxys 

 calcitrans conveys the infection in the Panama Canal Zone. 



Sander, <'?) in discussing surra in the Philippines, asserts that Stomoxys 

 calcitrans is proved by Curry in 1902 to be the carrier, and that this was 

 confirmed by Musgrave and Clegg. 



Leese,(2i) in discussing the comparative practical importance of Sto- 

 moxys as a surra transmitter, points out that, in an epizootic, Stomoxys 

 does not perform its work until the infection has already been introduced 

 by a more capable carrier like Tabanus which usually transports the or- 

 ganisms from a distance. Stomoxys transmits under these conditions at 

 close range, and usually among individuals in the same herd. 



Curry <22) found the trypanosomes of surra still active in the proboscides 

 and stomachs of Stomoxys calcitrans twenty-four hours after they had 

 bitten an infected animal. He believes that Stomoxys is alone responsible 

 for the propagation of surra in the Philippines. No experimental evidence 

 is advanced. 



Musgrave and Clegg (23) state in their report on surra in the Philippines, 

 that they transferred the infection to the monkey, horse, rat, dog, and 

 guinea pig by biting flies, in experiments so guarded as to make the results 

 absolutely conclusive. 



The inconclusiveness of the last reference is shown in the 

 fact that the species of biting fly concerned is not given, nor 

 are data of experimente involving procedure of method in ob- 

 taining results submitted. One is left to assume that the direct 

 mechanical method was applied and the biting fly i^sed was 

 Stomoxys calcitrans. These omissions are noticeable in con- 

 trast to the general excellence in the carefully compiled literature 

 and observations embodied in the remainder of the report. 



Bagshawe,(24) in commenting on the consensus of opinion of authorities 

 on surra, writes that it is generally assumed that flies act as mechanical 

 transmitters or accidental carriers, but, as far as he is aware, no experi- 

 ments are on record which prove or disprove it. This is before the 

 appearance of Leese's paper in 1911. 



MECHANICAL TRANSMISSION. 



That the principal and probably the only method by which 

 Stomoxys transmits the trypanosomes of surra and of other 



