550 
DIPTERA. 
Excluding the aquatic and some of the parasitic forms, the general 
appearance of the larva is much the same in the great majority of the 
species. The tail end is thick and blunt, bearing two chitinized patches 
marking the openings of the posterior spiracles : from the tail the body 
tapers toward the head, which is quite small, eyeless, and furnished with 
a pair of downward-curving hooklets which serve as jaws. The adults 
are nearly all flower-flies ; a few are predaceous and there are a small 
number of species which suck blood. 
If we except the Fleas, Mosquitos, Sand-flies, and perhaps some 
Midges, we may say that no Diptera appear to be nocturnal. Excepting 
the predators and blood-suckers, the adults frequent either flowers or 
filth. Hibernation where it occurs apparently takes place most often 
either in the larval or pupal condition, but sufficient information on this 
point has not yet been accumulated, and some flies (e.<7-, Mosquitos) 
