INJURIOUS INSECTS. 259 



the common house flics, the inner edge of one wing lapping over 

 that of the other. Another yet more distinctive mark is found in 

 the nerves or ribs of the wings- These are but three in number, 

 running lengthwise of the wing, diverging from each other as they 

 proceed backwards, and giving off no smaller or subordinate 

 branches or veins. In most of the species, these nerves termi- 

 nate before they reach the edge of the wing. This neuration of 

 the wings appears to distinguish the Cecidomyisc and Lestremiae 

 from all other insects, a genus of the Terrestrial Tipulides, named 

 Lasioptera, being the only one allied to them in this character, 

 I that possessing but two similar nervures. 



Other characters may be mentioned as more or less common to 

 ithe Cecidomyiae. The head is hemispherical in its form ; the pal- 

 pi or feelers are short and inconspicuous ; the eyes are crescent- 

 shaped ; the two first joints of the antennas are often perceptibly 

 jshorter than the others ; the wings are generally transparent, 

 shining and glass-like, reflecting the tints of the rainbow ; the 

 legs are long and slender ; the tarsi, or feet, consist of five joints, 

 lof which the first is quite short, and the second long. 



Habits. — The females of most of the species, have the body 

 iterminated by a sharp point ; in several, it is prolonged into a 

 tube or ovipositor, the joints of which shut into each other, like 

 those of a telescope. By this instrument, it is enabled to pierce 

 the young leaf or flower buds of trees or plants, and place one or 

 naore eggs therein. Each species is led by instinct to a particular 

 Dart of a certain kind of plant, which alone it selects as a home 

 'or its young. The egg hatches into a footless larva or maggot, 

 ;vhich subsists upon the juices, or upon the substance of the bud, 

 ind the irritation which it produces, causes an increased flow of 

 he fluids of the plant to this part, which thus grows to an extra- 

 )rdinary size, and forms a kind of excresence, called a gall. 

 They agree in this part of their habits, with the Cynips, a family 

 of four-winged flies, one of which produces the well known nut* 

 ^alls of commerce. In the interior of this excresence the maggot 

 Iwells, and having acquired its growth, it becomes a pupa, and 

 ike most other insects in this stage of their existence, takes no 

 ourishment, but lays dormant in its cell for a definite period of 

 ime, at the end of which, it changes to a fly, and makes its pas- 

 age out of the gall. Some of the species, probably, leave the 



