31 



Family 



TABANIDiE. 



(Horse-flies, or Breeze-flies, Dun-flies, Clegs and Stouts, frequently 

 called Gad-flies ; in Kent the species of Hceinatopota are locally known 



as Britnps.*) 



In the British Islands, as elsewhere, the horse-flies, owing to the 

 sizeof many of the species, are the most formidable in appearance of all 

 the blood-sucking Diptera. Indeed a large female of Tab aims sudeticics, 

 Zlr. (Plate 20), measuring nearly an inch in length, with a wing 

 expanse of over an inch and three-quarters, is exceeded in size by 

 but very few exotic species of this family, and frequently excites the 

 surprise of those who are not entomologists, when they learn that it 

 is really a British insect. The horse-flies, which are world-wide in 

 their distribution, are also among the largest of all families of Diptera, 

 the total number of species described at the end of the year 1904 

 being no less than 1,560. In the British Islands there are twenty-two 

 recognised species belonging to the genera Hcrinatopota, Thcrioplectes, 

 Atylotiis, Tabanus and Clirysops. Of Paiigonia (which, as regards 

 number of species, is the second of the principal genera of this family, 

 and is remarkable for the length of the proboscis, which, in some 

 species, greatly exceeds that of the body) there is no British 

 representative. 



In appearance the Tabanidai are bulky-bodied flies, with a large 

 head, which is convex in front and concave or flattened behind. In 

 the male the head is almost wholly composed of the eyes, which meet 

 together above in that sex but are separated in the female. The males 

 have an area in the upper portion of the eyes, varying in extent 

 according to the species, composed of larger facets than those below. 

 In life the eyes usually exhibit golden green or purple markings, which 

 are of value for the identification of species, and are especially brilliant 

 in the case of the females of Chrysops and Hamatopota, which, as pointed 



* ApiidF. V. Theobald, 'Second Report on Economic Zoology' (British Museum 

 (Natural History). London, 1904), p. i^. 



