C7 



Genus TABANUS Linnjcus. 

 Fauna Suecica, p. 402 (ITOI). 



In West Africa know n as " Mangrove-flies " ; elsciwiiere sometimes 

 called " Hippo-flies," and in the Anglo-Egyptian Sudan termed 

 "Seroots," or " Seruts." 



Plate V., fig. 35 — Plate XI., fig. 83. 



Wlien due allowance has been made for recognised synonyms, 

 and after deducting forms belonging to the Mediterranean Subregion, 

 the described African species of Tahanus at present number about 

 one hundred and twenty, forty-eight of which are figured in this 

 work. While there can be no doubt that many new species have 

 still to be discovered and described, it is also possible that further 

 researches may show that some of the names attached to species 

 included in the total mentioned are but synonyms. Owing to the 

 faultiness of many of the older descriptions, the paucity of plastic 

 characters, and the fact that the body-markings are for the most 

 part composed of fine hairs which are peculiarly liable to be rubbed 

 off, whereby the appearance of specimens becomes much altered, 

 it is often a matter of great difficulty to decide whether a given 

 species of Tahanus has or has not been already described. This 

 applies Avith especial force to species belonging to the T. secedens 

 group (Plate VII., figs. 54, 55, and Plate VIII., fig. 57) and certain 

 other groups of nearly allied and more or less obscurely marked 

 forms ; species with conspicuous wing-markings, such as are 

 exhibited by T. jasciatus and its allies (Plate V., fig. 30. and Plate 

 VI., figs. 40-43), are comparatively easy to identify. Wiien 

 distinguishing species or endeavouring to assign a number of 

 doubtful specimens to their proper species, special attention should 

 always be paid to the few plastic characters available. 'I'he most 

 important of these, which are situated ujion the head, are tlie 

 width and shape of the front (i.e.. the space between the eyes in the 

 female), the form of the frontal callus, and the shape of the terminal 



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