103 



Walk.) it widens out on the hind margins of the second and following 

 segments, so that its distal portion appears to be formed by a series 

 of truncated triangles. It is not surprising that such a species should 

 have been described under many different names, and in all 

 probability Tdbanus socius, Walk., T. macrops, Walk., T. 

 dorsivitta, Walk. (1854 nee 1850), and T. virgatus, Austen (nomen 

 novum for T. dorsivitta, Walk. nomen bis lectum), do not exhaust 

 the list of synonyms of T. tceniola, Pal. de Beauv. Tabanus variatus, 

 Walk, (see below, p. 105, Plate VIII., fig. 59), in which the modi- 

 fication of the median abdominal stripe into a series of triangles, 

 with their bases resting on the hind margins of the segments, is 

 carried still further, is perhaps also a form of T. tceniola, Pal. de 

 Beauv., although for the present it is more convenient to continue 

 to regard it as a distinct species. 



In many localities Tabanus tceniola would appear to be extremely 

 abundant, and the form socius is one of the commonest " seroot- 

 flies " on the White Nile ; the species is represented in almost 

 every consignment of African blood-sucking flies received at the 

 Museum, and the National Collection already contains nearly two 

 hundred examples of this insect. The area of distribution of the 

 species being so extraordinarily wide, it is unnecessary to go into 

 details with regard to these specimens, but a few general notes may 

 be added. 



In French Congo, according to Roubaud,* Tabanus tceniola is 

 of general occurrence though local, and only a small number of 

 individuals are found together ; in the region of Lake Chad the 

 species is known to the natives as N'gaya Illi, or Ter Azarak.* The 

 type of Tabanus macrops, Walk., which is from Egypt, is a male, 

 and it is interesting to observe that out of fourteen specimens 

 recently received from the Kharga Oasis, Upper Egypt, July and 

 September, 1907 (the late Dr. H. H. Baker), no fewer than eleven are 

 males : with the exception of one other specimen of this sex, from Keffi, 

 Nassarawa Province, Northern Nigeria, May 3rd, 1907 (Dr. R. F. 

 Williams], these are the only males of T. tceniola that have been 



* Gf. Surcouf and Roubaud, Bulletin du Museum National d 'Histoire Naturelle, 

 Ann6e 1908, No. 5 (Paris, 1908). 



