DIPTERA. 497 



ochre-yellow hairs, intermixed with which there are a few 

 black brit>ties; and there is a faint blackish line on the top of 

 tile first pair of thighs. A few black bristles are scattered upon 

 the head and the top of the thorax. The bristle of the an- 

 tennae, when viewed with a powerful magnifier, is found to be 

 covered with very minute hairs. 



Some two-winged tlies deposit their eggs in the steins, buds, 

 and leaves of plants, thereby producing large tumors or galls, 

 wherein their young reside. Others lay their eggs in fruits, on 

 the pulp of which their maggots live. These gall and fruit 

 flies belong to a family called Ortalidians (Ortalidid.e), from 

 a word signifying to flap or shake the wings; for they keep 

 their wings in motion nearly all the time, jerking them up and 

 down, and twisting them round so that the thick outer edges 

 often come together. Some of them are in the habit of sud- 

 denly raising their wings perpendicularly above their backs, 

 and running along a few steps with them spread like the tail of 

 a peacock. These insects, together with several other gToups 

 of flies, differ from all the foregoing in many respects, although 

 they agree with them in their transformations. The forehead 

 is broad in both sexes; their winglets are very small or entirely 

 wanting; their powers of flight are feeble; and they are rarely 

 found sporting on flowers in the sunshine, but seem generally 

 to prefer shady and damp places. The wings of the Ortalidi- 

 ans are often beautifully variegated, striped, or spotted with 

 shades of brown or black. The hind body in the female gen- 

 erally ends with a pointed tube, w^herewith the eggs are depos- 

 ited. The little white maggots often found in over ripe whor- 

 tleberries, raspberries, cherries, and other fruits, are the young 

 of some of these insects. Swellings, or galls, as large as a 

 walnut, are often seen on the stems of some of our native 

 Asters or starworts. They are caused by the punctures of a 

 fly, which lays its eggs, singly, in the stem, when the latter 

 is tender. The puncture is followed by a spongy swelling, 

 wherein the maggot, hatched from the egg, lives, and passes 

 through its transformations. The insect finally comes out in 

 the fly state, through a small hole previously made in the gall 

 by the maggot.. This fly may be called the gall-fly of the star- 

 63 



