61 
Contains the horse-flies (Tabynidce) , robber-flies ( Asilidce ), 
etc. 
C. Antennae with only two or three joints, terminated by a 
bristle; proboscis generally concealed in the oral cavity; 
with two lancets (four in iSyrphidce); pupa coarctate, the 
skin of the larva forming an oval case. 
The Syrphus-flies or Sweat-bees ( Syrphidoe ); house-flies 
Mnscidce ); the bot-flies ( CEstridce ), etc. 
Sect. II. Head immersed in the thorax; claws denticulated or fur¬ 
nished with minute teeth; larva nourished in the abdomen 
of the mother until it passes into the pupa state. 
Bot-ticks ( Nycteribidce ), bee-lice ( Braulina ); forest-flies or 
horse-ticks and sheep-ticks (Hippoboscidaz ). 
The fleas ( Pulicidce ), which Westwood places in a separate order, 
are now usually included among the Diptera. 
The family CEstridce, as stated above, includes the various species 
of bot-flies. One of the most noted of these is CEstrus ovis L ., or the 
Sheep bot-fly. 
The family ( CEstridce ,) which contains the hot and breeze flies, is 
very singular in some respects. Although in general appearance 
somewhat resembling a common house-fly, yet the difference is suffi¬ 
cient to be noticed at a glance by the unscientific observer. As a 
general rule, the body of the fly is stout and hairy, somewhat like 
that of humble bees. Their mouth is very imperfectly developed. In 
the sheep bot-fly this organ is so reduced that it is impossible for the 
insect in its perfect, or fly state, to take nourishment, showing thereby 
that it was intended by Nature that its period of imbibing food should 
be confined to its larval or maggot state. The larvae of these insects 
are generally thick, fleshy, footless maggots or worms, which have 
the hinder margins of the segments or rings of the body furnished 
with minute spines, which point backward, enabling them to move 
readily in the confined situations in which they reside. The head is 
usually very small, and the mouth in some consists simply of fleshy 
tubercles, as those which reside in the skin of animals, while in those 
species which reside in the stomach and nostrils, it is furnished with 
two little hooks, by means of which they are enabled to hold on to 
their positions. Their great peculiarity consists in the strange situa¬ 
tions they select to pass their larval state, which is the most impor¬ 
tant part of their existence, their perfect state being devoted wholly 
to propagation. The Gastrophilus equi, or horse bot-fly, selects the 
stomach of the horse as the abode of its larva,—Nature having fur¬ 
nished it with that instinct which directs it where to deposit its 
eggs, that they may be carried to the spot where the larva will be 
developed and find suitable nourishment. 
The CEstrus ovis , or sheep bot-fly, on the contrary, selects the nos¬ 
trils of its victims as the most appropriate place to plant its offspring. 
The Hypoderrtia bovis , or ox bot-fly, plants its eggs in the skin of 
cattle, where they form tumors, in which the larvae dwell. Another 
species of this same genus (the Ilypoderma tarandi) is found in the 
skin of the reindeer. 
The species of Cuterebra inhabit the internal organs of squirrels, 
rabbits, mice and other small animals. Other species infest dogs and 
other quadrupeds, and even the frog is said to have its bot-fly. Nor 
is man himself wholly exempt from their attacks. 
