40 



dorsal ridge, which may exhibit a depression in the median hne 

 partially dividing it into two, a rounded tubercle on each side, and 

 four similar ventral ones. The last segment bears a terminal conical 

 retractile prolongation, containing the stigmata or respiratory 

 apertures in a vertical slit, while on the ventral side the anus is 

 situate between a pair of prominent tumid lips, Tabanid larvse 

 live in water, wet sand or mud, earth or decaying vegetable matter ; 

 they are carnivorous, and prey upon snails, beetle-larvse, small 

 Crustaceans, worms, etc. The pupa, which is not unlike that of a 

 Lepidopterous insect, and in colour dull yellowish or some shade of 

 brown, remains stationary, and is usually found in earth or damp 

 rubbish at the edge of water. The thorax bears a pair of somewhat 

 ear-shaped spiracular prominences ; each abdominal segment is 

 encircled with a ring of slender spines on its distal tliird, and there 

 are six sharp spines or teeth at the tip of the terminal segment. 



So far as present knowledge goes, there is no 



Tabanidae and reason to regard Tabanidse as regular carriers of 



Disease. any form of disease among human beings, although 



it is obvious that these flies, like any other blood- 

 sucking Diptera, may occasionally convey pathogenic organisms, 

 such as Trypanosoma gambiense or Bacillus anthracis* With 

 respect to domestic animals, however, the matter would seem to 

 rest on a somewhat different footing, for Tabanidae as a whole may 

 be considered as pests of animals more than of human beings, and 

 the relatively considerable amount of blood that many of these flies 

 are able to imbibe, owing to their large size, obviously increases 

 the risk of their sucking up micro-organisms from infected animals. 

 It will be seen from the statements under the heading " Tahanus and 



* Dr. Arthur Pearson, P.M.O., Union Mini ere du Haut-Katanga, writing from 

 Ruwe, Katanga District, Congo Free State, August 3rd, 1908 (Brit. Med. Journal, 

 October 17th, 1908, p. 1218) on "Sleeping Sickness," says :—" With regard to the 

 possibility that other biting flies, such as Tabanidre, may infect, to my mind one 

 may point to the fact that, whereas these are apparently distributed all over the 

 country, and for three months of the year are so plentiful as to be productive 

 of very considerable discomfort even to a clothed European, the disease has confined 

 itself strictly to the riparian population on those rivers where [Olossina] palpalis is 

 found. Surely this evidence is very powerful ... I do not deny, of course, the 

 possibility of infection when one of the Tabanidce, interrupted in its feed on an 

 infected native, plunges its still wet {iroboscis into an uninfected man. But such 

 cases must be very rare, judging from results." 



