302 STOMOXYS AND DISEASE [CH. 



Bouffard at Bamako on the Upper Niger experimented on 

 the transmission of Souma, a trypanosomiasis of cattle caused 

 by T. cazalboui (vide p. 335). A calf was inoculated with this 

 parasite and shewed numerous t^panosomes in its blood on the 

 eighth day. A healthy calf was then segregated with the other 

 calf in a fly-proof stable, the animals being separated by a 

 distance of one and a half metres. Forty wild Stomoxys were 

 then put in the stable and were observed to feed on two after- 

 noons, after which they died. Twelve days later trypanosomes 

 appeared in the blood of the healthy calf so that it seems 

 evident that Stomoxys is able to carry T. cazalboui. Whether 

 the flies were naturally infected or not when caught, was not 

 decided. 



In French West Africa, Bouet and Roubaud succeeded 

 with difficulty in the direct transmission of T.' cazalboui and 

 T. pecaudi by means of Stomoxys, but failed to transmit 

 T. dimorphon. On the other hand, the trypanosomes of the 

 Sahara were easily transmitted by means of this insect as shewn 

 by their results. Employing T. soudanense, out of five experi- 

 ments performed under laboratory conditions, with no intervals 

 between the bites of the flies, four gave positive results. In 

 another experiment at least 24 hours were allowed to elapse 

 between the feed on the infected and on the healthy animal, in 

 this case a dog. This animal became infected a month later 

 shewing that the flies were still infective after 24 hours. In 

 addition one experiment was made under natural conditions. 

 A healthy puppy from which all ectoparasites had been carefully 

 removed was kept on a chain during the day beside an infected 

 dog in a place infested with Stomoxys ( ? calcitrans and nigra) ; 

 at night it was removed and placed in a fly-proof cage to 

 prevent any nocturnal flies feeding on it. The experiment 

 lasted from the nth to the igth of August and both animals 

 were frequently bitten by Stomoxys. On August 24th the 

 puppy became infected. 



The results were similar on employing a strain of T. evansi 

 (Surra) obtained from some camels at St Louis. In three 

 experiments the Stomoxys were transferred from an infected to a 

 healthy rat and a minute later to another healthy rat. In two 



