CHARACTERISTICS OF FAMILIES OF DIPTERA. wii 
Clypeus rudimentary. Middle tibiz with spurs. Ovipositor con- 
sists of three joints and is horny and flat. 
Family Sapromyzide. 
Auxiliary vein as in the preceding, frequently very much approxi- 
mated to the first longitudinal vein. Costa without bristles or 
marginal spine. Posterior basal ceils small. No peculiar hairs on 
the longitudinal veins. Front with a single row of bristles on each 
side. Only the middle tibiz have terminal spurs; all have the 
small erect bristles. Ovipositor not horny. 
Family Heteroneuride. 
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 Opomyzide. 
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 alulze wanting. Front with stout bristles above 
Border of mouth pubescent and with long hairs. Palpi small. 
Family Sepside. 
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 Piophilide. 
Front with some small bristles above only. A vibrissa on each 
side of the border of the mouth. Abdomen often petiolate and 
curved. Auxiliary vein coalescent with the first longitudinal vein 
along its whole length. 
Family Geomyzide. 
Front with stout bristles above. Border of the mouth with 
vibrissze. Bristles along costa. First longitudinal very short, the 
auxiliary separated from it only near base. Posterior basal cells very 
small. All the tibize having an erect hair on the outer side before 
the tip. 
b 
