insects injurious to man and stock in zanzibar. 397 



Tabanidae. 



Many species of these flies have been taken from various districts in both islands 

 (Zanzibar and Pemba). They are found in abundance in wooded areas close to 

 streams or marshes. I have captured very few species in open arid or grassy country. 

 One record exists of a capture of two Tabamis biguttalus in the Government stables 

 in the town. Their prevalence varies with the seasons, and they are very abimdant 

 for about six weeks after the rains. Ideal weather conditions are slight showers 

 of rain with sunny interludes ; on such a day the bag is always full. During heavy 

 rain or high wind they are conspicuous by their absence. 



Tabanidae have not been definitely implicated in the spread of disease in Zanzibar, 

 but there is a certain amount of evidence that they are capable of acting as vectors 

 of Trypanosoma pecorutn, the common trypanosome of stock in the island. Repeated 

 efforts have been made to prove this experimentally ; but owing to the extreme 

 difficulty of keeping these flies alive in capti\'ity and inducing them to bite experi- 

 mental animals, no results have been forthcoming. 



Tabanus taeniola, P. de B. This is the commonest Tabanid in the two islands, 

 being found everywhere. They often attack man, flying on board the mail steamer 

 while anchored at Pemba and inflicting severe bites on the passengers and crew. 

 When alighting on cattle they nearly always select the lumbar region, seldom the 

 legs. Engorgement averages 2| to 3 minutes. In mixed herds of cattle and 

 domesticated buffaloes the latter are always singled out for attack, as they seem 

 more callous to the bites. 



Tabamis taeniola var. variatus, Walk. This variety has only been taken occa- 

 sionally, the typical T. taeniola being the common form. 



Tabanus fmtermis, Macq. A very common species, being found throughout the 

 two islands. They often attack man, their feeding habits being like those of 

 T. taeniola. 



Tabanus par. Walk. This small species has a wide distribution throughout the two 

 islands. It nearly always feeds on the withers and hocks of cattle. 



Tabanus gratus, Lw. Quite a common species ; large numbers have been taken 

 in various districts on both islands. 



Tabanus africanus, Gray. This handsome insect is by no means common, and 

 its distribution and prevalence seem to be influenced both by season and environ- 

 ment. All records of capture are shortly after the rains and only in districts where 

 streams are prevalent. 



Tabanus biguttalus, Wied. A common species. It generally feeds on the hump 

 of cattle, seldom attacking any other part. Engorgement in some cases took ^h 

 minutes. Males were taken on tree-trunks in proximity to grazing groimds. 



Tabanus conspicuus, Ric. A rare species ; only one female has been taken. 



Tabanus thoracinus, P. de B. An uncommon form ; our collection comprises 

 only four specimens. 



Tabanus ditaeniatus, Macq. Nowhere very abundant ; all our specimens were 

 taken shortly after the rains. 



Tabanus leucostmnus, Lw. Represented by two females in our collection. 



