CHA RA CTERIS TICS O F FA MI LIES OF DIPTERA . x vii 



Clypeus rudimentary. Middle tibi?s with spurs. Ovipositor con- 

 sists of three joints and is horny and flat. 



Family Sapromyzidce. 



Auxiliary vein as in the preceding, frequently very much approxi- 

 mated to the first longitudinal vein. Costa without bristles or 

 marginal spine. Posterior basal cells small. No peculiar hairs on 

 the longitudinal veins. Front with a single row of bristles on each 

 side. Only the middle tibic'e have terminal spurs ; all have the 

 small erect bristles. Ovipositor not horny. 



Farriily Heterojieurida . 



First longitudinal vein short, auxiliary very much approximated to 

 it. No bristles on costa. Basal cells small. Front with long 

 bristles. A vibrissa on the border of the mouth at each side. 

 Palpi large. Legs slender. Middle and posterior tarsi with spurs. 



Family Opoiiiyzidcc. 



First longitudinal vein much abbreviated ; the auxiliary becomes 

 obsolete before reaching completely the first longitudinal vein ; the 

 latter sends out before its end, towards the costa, a branch, which 

 may be considered as the end of the auxiliary vein. Basal cells small. 

 Axillary incision and alulae wanting. Front with stout bristles above 

 Border of mouth pubescent and with long hairs. Palpi small. 



Family Sepsidce. 



Auxiliary vein distinctly separated from the first longitudinal veins. 

 Posterior basal cells large. Head rounded. Front bristly. Border 

 of mouth more or less hairy, the foremost hair often imitating a 

 vibrissa. 



Family Piophilidce. 



Front with some small bristles above only, A vibrissa on each 

 side of the border of the mouth. x\bdomen often petiolate and 

 curved. Auxiliary vein coalescent with the first longitudinal vein 

 along its whole length. 



Family Geomyzidce. 



Front with stout bristles above. Border of the mouth with 

 vibrissce. Bristles along costa. First longitudinal very short, the 

 auxiliary separated from it only near base. Posterior basal cells very 

 small. All the tibite having an erect hair on the outer side before 

 the tip. 



b 



