322 



The Two-winged Flies 



Next to the mosquitoes, the worst pests among the nematocerous flies are 

 various species of the gall-midge family, Cecidomyida:, a family in which 

 all the stages, larval, pupal, and adult, of all the species are terrestrial. The 



gall -midges are the frailest, 



smallest, and least conspicuous 



""X^ / of all the flies, but their great 



numbers and vegetable feeding 



Fig. 449. Fig. 450. 



Fig. 44g. — The giant crane-fly, Holorusia rubiginosa, male. (Three-fourths natural 



size.) 

 Fig. 450. — Larva (at left) and pupa (at right) of giant crane-fly, Holorusia rubiginosa; 



in middle of figure enlarged posterior aspect of larval body, showing spiracles. 



(Larva and pupa three-fourths natural size.) 



and gall-making habits make them formidable enemies of many of our 

 cultivated plants. The tremendous aggregate losses suffered by the wheat- 

 growers of this countr)- from the ravages of the Hessian fly, the damage 

 to clover-fields by the clover-leaf and clover-seed midges, and the injuring 

 or killing of thousands of pine-trees from the attacks of the minute 

 pine Diplo-sids, are evidences of the great economic importance of the 

 delicate little gall-gnats. About one hundred species are known in this 

 country, and of these most are more or less destructive to cultivated herbs, 

 shrubs, or trees. 



The tiny bodies of the flies are usually covered with fme hair, easily 

 rubbed off, and the antennae bear whorls of larger hairs, which, with some 

 species, are attached by both ends, thus making little hair loops. The 

 minute eggs, reddish or white, are usually deposited in or on growing plant- 

 tissue, and the little footless, headless, maggot-like larvae probably derive 

 most of their food by imbibing it through the skin. Lying with the body 



