450 INSECTS INJURIOUS TO VEGETATION. 



The far-famed Hessian fly and the wheat-fly of Europe, and 

 of this country, are small gnats or midges, and belong to the 

 family called Cecidomyiad.e, or gall-gnats. The insects of 

 this family are very numerous, and most of them, in the mag- 

 got state, live in galls or unnatural enlargements of the stems, 

 leaves, and buds of plants, caused by the punctures of the 

 winged insects in laying their eggs, or by the irritation of the 

 maggots hatched therefrom. The Hessian fly, wheat-fly, and 

 some others, differ from the majority in not producing such 

 alterations in plants. The proboscis of these insects is very 

 short, and does not contain the piercing bristles found in the 

 long proboscis of the biting gnats and mosquitos. Their an- 

 tennae are long, composed of many little, bead-like joints, which 

 are more distant in the males than in the other sex ; and each 

 joint is surrounded with short hairs. Their eyes are kidney- 

 shaped. Their legs arc rather long and very slender. Their 

 wings have only two, three, or four veins in them, and are 

 fringed with little hairs around the edges; when not in use, 

 they are generally carried flat on the back. The hind body of 

 the females often ends with a retractile, conical tube, where- 

 with they deposit their eggs. Their young are little, footless 

 maggots, tapering at each end, and generally of a deep yellow 

 or orange color. They live on the juices of plants, and un- 

 dergo their transformations either in these plants, or in the 

 ground. 



The transformations of these insects offer some peculiarities 

 that do not seem to have been described by European natu- 

 ralists, and probably are not well understood by them. Three 

 modifications in the process have been observed in this coun- 

 try, and examples of these are afforded by Cecidomyia Salicis, 

 destructor, and Tritici. In all of them the pupa has the limbs 

 and wings free or unconfined, and becomes active shortly 

 before its final change, being enabled to crawl out of the place 

 where it had hitherto lodged, when about to take the winged 

 form. It appears also that these Cecidomyians retain the 

 larva-skin when the insect is changed to a pupa; this skin 

 undergoing only certain alterations in the course of the pro- 

 cess, without being thrown off. The abdominal part of the 



