3 22 
The Two-winged Flies 
Next to the mosquitoes, the worst pests among the nematocerous flies are 
various species of the gall-midge family, Cecidomyidae, 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 
of all the flies, but their great 
numbers and vegetable feeding 
Fig. 449. 
Fig. 450. 
Fig. 449.—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 country 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 Diplosids, 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 fine 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 
