364 MEDICAL ENTOMOLOGY 



infected healthy monkeys with a culture obtained from those which had 

 acquired the disease as the result of being bitten by this species. 

 As this work is still in progress no comment is called for at present. 



Stomoxys calcitrans has long been suspected of being the carrier of 

 the trypanosome of Surra (T. evansi) and probably of other animal 

 trypanosomes, but the evidence is so far inconclusive. Mitzmain has 

 recently carried out a long series of experiments with this fly in order to 

 settle this question. His results indicate that Trypanosoma evansi does 

 not develop in Stomoxys calcitrans, and that it plays no part in the 

 transmission of the parasite. 



As is well known, this species chiefly bites cattle, horses, mules and 

 donkeys, though it will occasionally bite man. If one stands near an 

 animal on which a number of the flies are feeding one or more will bite 

 about the ankles, even through thick socks. The other species the habits 

 of which are known behave in the same way. 



In Manila Mitzmain notes that Stomoxys calcitrans bites man shortly 

 after the atmosphere has been cooled by a shower of rain, and at those 

 seasons of the year when it is unusually abundant. He records the in- 

 stance of a female coming into the laboratory after a shower of rain and 

 alighting on his arm and sucking blood. Within an hour another 

 settled close to the first one and also sucked blood ; in this way al- 

 together five flies attacked him, and it is interesting to note that three 

 of them were males. 



The flies are most abundant about stable and farm yards, and they 

 may be seen basking in the sun on railings, the leaves of plants and 

 blades of grass, especially where cattle are grazing. In Madras it is 

 common during the cold weather ; it never bites much before 9 a.m. 

 The males may be seen hovering for short periods, darting at each other 

 and then returning to the body of the animal or a neighbouring twig. 



Portschinski appears to be the first observer to have made a de- 

 tailed study of the life history of Stomoxys calcitrans ; he confirmed 

 the earlier observations of Bouche, who discovered 



StomMysTalcitl'ans the larvae in stable manure - Later Howard and 

 Merlett repeated these observations, and bred the 

 flies out of larvae collected in horse manure. In 1906 Newstead gave 

 an account of the life history of Stomoxys calcitrans as observed in 

 Liverpool and Chester. A most complete study of the early stages of 

 this fly has recently been published by Mitzmain. The summary of 

 the life history of Stomoxys calcitrans given here is taken from the 

 papers of these two authors. 



