6 BRITISH FLIES 



Head, thorax, margin of scutellum, and legs without any niacrochietse, 

 unless the bristles which occur in the Mycctoioliilidm may be considered 

 such ; but Osten Sacken is of opinion that they are not true macrochsette, 

 and in that family the palpi, antennae, and venation locate them at once. 

 Pubescence never dense and erect. 



In all cases of doubt as to whether a fly belongs to the Nemoceka 

 through the palpi being only one- or two-jointed (as in Aedes or some 

 genera of Gecidomyidai), the structure of the antennae and the venation 

 should remove all doubt. When the antennae are shortened and the 

 llagellum (= third joint) is apparently only annulated (as in the 

 Bihionidce, SimvMdce, or Rhyphidce), then the antennae never bear any 

 terminal style or arista, and the venation is either completely distinct 

 from any of the Brachycera, or if rather similar to that of the 

 Bkaciiycera (as in Bhyphus) the widened end of the anal cell deter- 

 mines its position, and in these cases the many-jointed pendulous palpi 

 are distinct. 



lirauer gives the following characters for the larvae of the Nemoceka, 

 as distincruishing them from those of the Brachycera : " Larvae with 

 "horizontally 1)iting upper jaws; or with the mouth parts quite rudi- 

 " mentary, in which case the larvae are peripneustic and have 13 

 " segments." 



BEACHYCEKA. 



Palpi porrect (not pendulous), one- or two-jointed (sometimes rudi- 

 mentary); if two-jointed the second joint is more or less clavate, 

 and larger than the first which appears to be a handle to the second 

 joint. 



Antennae after the two basal joints (of which the first is sometimes so 

 small as to be practically imperceptible) with a third joint (or fiagellum) 

 of most varied structure (though similar in both sexes), but which is most 



commonly a solid joint with an apical 

 (or sometimes dorsal) style or arista. 

 This joint may be annulated to such 

 an extent that it resembles the 

 fiagellum of some of the Nemocera, 

 as for instance in Xylophagus (fig. 11), 

 or Hcxatoma (fig. 17), or Cmnomyia 

 (fig. 18), or even as in the oxtra- 

 vvc.i-i.^iuxaiomapMuccns i. x 13. Ordinary Mavhiccrvs (fig. 12), and in 



these cases there is no terminal style 

 or arista, but the venation (especially the anal cell) and the porrect palpi 

 at once separate them from the Nemocera ; others have this third joint 

 very difforent from the two basal joints but still annulated, though the 



