642 
DIPTERA. 
that because the treatment is superficial the families are therefore un¬ 
important. Leaving the (Estridce for the present, we will begin with the 
three families Tachinidce, Sarcophagidce and Muscidce. Taken as a 
whole they are moderately large, more or less bristly, grey blackish or 
blue flies ; many have the general appearance of house-flies or blue¬ 
bottles : they are distinguished as follows :— 
Arista bare. Upper side of abdomen generally 
bristly on the basal segments. 
Larvae parasitic . . .. .. Tachinidce. 
Arista bare at the end, but with hairs on the 
basal half. Basal segments of abdomen gener¬ 
ally without strong bristles. Larvae parasitic 
or scavengers .. . . .. .. Sarcophagidce. 
Arista, on at least one side, hairy or plumose 
along its whole length. Abdomen generally 
smooth, not bristly on the basal part. Larvae 
mostly scavengers . . .. .. Muscidce. 
(If like this, and with strong, horny, more or less 
elongated proboscis, hut with 1st posterior cell 
open as in Anthomyiids) . . .. “ Biting ’ ’ Mus¬ 
cidce (See pp. 
645, 659). 
Muscidce. 
Rather small compactly-built flies. The abdomen of four visible seg¬ 
ments , not bristly on its basal part, and not swollen at the tip in the 
males as in Sarcophagidce. The antennal arista plumose to the tip 
at least on one side. posterior cell closed or much narrowed 
except in some of the blood-sucking species where it is only slightly 
narrowed ; eyes in males much nearer together than in females, often 
touching. 
This family comprises those house-flies, blue-bottles and blow-flies 
which are familiar insects wherever man has made his home, and also, 
be it remarked, where he has not. Almost all the very numerous 
species may be said to closely resemble in colour and general appearance 
one of these two types, the house-fly or the blue-bottle. The life- 
history is short, a fair average period for the commoner species being 10 
to 15 days, but this is subject to considerable variation with food and 
