622 DIPTERA. 



their history lias 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 larvas 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 CEsTRiDJE, so named from the 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 larvae 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 



