2o8 INJURIOUS AND USEFUL INSECTS 



family of minute and delicate Nemoceran flies, with long, 

 thread-like or beaded antenna, 13-jointed in the female, 

 29-36-jointed in the male, where they may be as long 

 as the body, and furnished with conspicuous whorls of 

 hairs. The proboscis is short, the wings relatively large, few- 

 veined, and fringed, the legs very long and slender, adapted for 

 running. The end of the female abdomen is drawn out into a 

 long, jointed extremity (inaccurately described as an ovipositor) 

 which can be grasped by the large and hooked claspers of the 

 male. The eggs are very few and large. 



In the larval stage the gall-midges are remarkable for their 

 very diverse mode of life. Some simply feed on leaves or 

 bark ; others make galls upon a great variety of plants ; or 

 subsist upon the galls made by other insects ; a few prey upon 

 aphids, acari, and other small animals. The larvae are 

 usually red, orange, or yellow, the body is often flattened, 

 narrowed at both ends, and apparently composed of more 

 than the usual number of segments. This is probably due 

 to the retractile head, which can be completely withdrawn 

 into the body, when the fore part of the body-wall becomes 

 infolded. One or more transverse folds are thus produced, 

 which give an appearance of additional segments. From the 

 ventral surface of the prothorax a chitinous spine projects, 

 which is nearly always forked, but sometimes ends in a simple 

 point ; in some larvae this can be used like a foot in reversing 

 the position of the body ; perhaps, in other species, it may be 

 opposable to the head. False feet may be present on the 

 abdomen, but they are generally absent. A number of the 

 spiracles are open. The larvae are never aquatic ; some are 

 capable of viviparous reproduction, though still unprovided 

 with sexual organs of the ordinary kind. In many the larval 

 skin is not cast at pupation, but hardens over the pup»; 

 in others the larval skin is cast, and the pupa is protected 

 only by a silken cocoon. To this family belongs the Hessian- 

 fly (see Lesson 27). 



The wheat-midge (Cecidomyia tritici) lays eggs in the 

 flowers of wheat, by means of the long and slender tip of the 

 abdomen (the so-called ovipositor). The larvae feed a number 

 together on the growing grain, and are often called from their 

 colour red maggots. They pupate in the earth or in the husk, 

 and the flies appear in the following season. 



