ROLE OF STOMOXYS CALCITRANS. 499 



as no great stress was laid on microscopical findings. Emul- 

 sions from dissected flies fed on surra blood did, however, show 

 organisms resembling Trypanosoma evansi. In the following 

 experiments house flies were employed which had emerged April 

 23 and 24, 1912, from laboratory cultures. A large number of 

 these were applied to the abraded tail of a surra-infected monkey, 

 and three hours later an emulsion from 3 flies was found swarm- 

 ing with trypanosomes. At this time 20 flies of the lot were 

 inoculated into 2 guinea pigs, the abdominal contents only being 

 used. Stained smears of the solution that was inoculated re- 

 vealed the presence in moderate numbers of organisms indis- 

 tinguishable from Tr. evansi. 



The two inoculated guinea pigs, 127 and 128, were found 

 to be infected on the seventh and eighth days respectively. Both 

 showed trypanosomes on numerous occasions and also at death, 

 which occurred on the sixty-fifth day after inoculation in the case 

 of No. 127, and on the fifty-second day in the case of No. 128. 



Two hundred fifty flies of this lot were utilized in carrying 

 through the following experiment. Prior to infection of the 

 house flies, 200 Stomoxys were placed on a surra monkey's 

 tail (which had not been previously abraded). After thirty 

 minutes the majority of the flies had fed, and then a fresh bottle, 

 containing the 250 Musca, was substituted. The house flies fed 

 ravenously on the blood brought to the surface by the probes 

 of the first flies. When a large number of the Musca showed 

 partly blood-engorged abdomens, which occurred in fifteen min- 

 utes, they were withdrawn and applied to a healthy monkey 

 after 200 hungry, newly emerged Stomoxys were turned loose 

 in the same bottle, both species being. then applied to the tail 

 of the fresh monkey. Here the attempts to simulate natural 

 conditions were successful; the Musca fed after the Stomoxys, 

 lapping the fluid from punctures made by the latter. The flies 

 were not disturbed until all were apparently satisfied, which was 

 a matter of forty minutes. 



In a second experiment 30 laboratory-bred flies were applied 

 to a healthy monkey and 25 bites were recorded. Immediately 

 50 Musca which had fed from a fresh wound on a surra animal 

 were substituted for the Stomoxys. In twenty minutes 30 to 

 40 of the Musca had lapped blood from the healthy monkey's 

 tail. Full opportunity was given them to carry infected material 

 on labella and pulvillus into the wounds presented. Three other 

 experiments were conducted with guinea pigs as hosts. In one, 

 40 Musca accompanied 20 Stomoxys; in another, 14 Stomoxys 

 and 80 Musca were used; and in the last, 20 Stomoxys were 



