DIPTERA. 
622 
their history has not yet been investigated, and the insects 
have not been scientifically examined and described. From 
the somewhat vague accounts that have been given of them, 
it is evident that they are much too large for any of the 
parasitical insects which attack the larvse and eggs of the 
Hessian and wheat flies ; and they appear sometimes to have 
been mistaken for ‘the latter. In an extract from a paper 
by Mr. Worth, on the Hessian fly, mention is made of a 
pale yellow worm (maggot), about three sixteenths of an 
inch long, having been found by him within the stalks 
of wheat near the root, where its presence was detected 
by a swelling of the part attacked. This was perhaps the 
larva of one of the Oscinians. A careful examination of 
all the insects that inhabit our fields of grain is very much 
wanted. 
The various insects, improperly called bot-bees, are two¬ 
winged flies, and belong to the order Diptera, and the fam¬ 
ily CEstrid^, so named from tlie principal genus in it. 
Bot-flies do not seem to have any mouth or proboscis; for 
although these parts do really exist in them, the opening 
of the mouth is extremely small, and the proboscis is very 
short, and is entirely concealed in it; so that these insects, 
while in the winged state, do not appear to be able to take 
any nourishment. They somewhat resemble the Syrphians 
in form and color, and in the large size of their heads; 
but the eyes are proportionally small, and there is a large 
space between them. The face is swollen or puffed out 
before. The antennae are very short, and almost buried 
in two little holes, close together, on the forehead. The 
winglets are large and entirely cover the poisers. The 
hind body of the females ends with a conical tube, bent 
under the body, and used for depositing the eggs, which 
the insect lays whilst flying. The larvse or young of bot¬ 
flies live in various parts of the bodies of animals. They 
are thick, fleshy, whitish maggots, without feet, tapering 
towards the head, which is generally armed with two 
