224 ORTHORRHAPHA BRACHYCERA [CH. 



No6, G. (1901). Sul circlo evolutive della Filaria bancrofti (Cobbold) 

 e della Filaria immitis (Leidy). Ric. /. n. laboroi. d. anatomia 

 normale d. R. Univ. di Roma, vol. viii. pp. 275-353. 



(1903). Ulteriori studi suUa Filaria immitis. Rend. Ace. d. 



Lincei. vol. xii. pp. 476-483. 



Shipley, A. E. (1896). Nemathelminthes and Chaetognatha, in Cam- 

 bridge Natural History. London : Macmillan and Co. 



CHAPTER XIII 



ORTHORRHAPHA BRACHYCERA 



The flies belonging to this series are characterised by the 

 form of the antennae, which, although variable, are never truly 

 Nematocerous, nor yet like those of the Cyciorrhapha. They 

 are usually composed of three dissimilar segments, of which 

 the third is sometimes elongate and subdivided into a number 

 of indistinctly separated segments. When an arista is present 

 it is always terminal in position, and never superior as in the 

 Cyciorrhapha. Rarely, as in the Leptidae, the antennae may 

 be divided into more than three segments. The palpi are one- 

 or two-jointed. Around the base of the antennae there is 

 no definite arched suture enclosing a small depressed space, 

 as in the Cyciorrhapha Schizophora. The venation of the 

 wings is usually more complex than that of any of the other 

 divisions ; the second longitudinal vein is simple, but the third 

 and fourth veins are often forked. The anal cell is closed 

 before the border of the wing, or distinctly narrowed at the 

 border. A discal cell is practically always present. 



This group includes 16 families of flies, of which only one — 

 the Tabanidae — is of any interest from the present point of 

 view. Two other families, the Leptidae and Asilidae, include 

 a few blood-sucking species, but are of little importance. As, 

 however, many of the species belonging to these and other 

 families, are habitually predacious on insects, they have an 

 economic interest, and therefore we append the following 

 synopsis. The only one of these families that includes species 

 known to carry disease is the Tabanidae. 



