444 
THE STUDY OF INSECTS\ 
four to six deep. The larvae crawl over each other so that 
the column advances about an inch a minute. 
Family CECIDOMYIID^: (Cec-i-do-my-i'i-dae). 
The Gall-gnats . 
The gall-gnats are minute flies which are extremely 
delicate in structure. The body and wings are clothed with 
long hairs, which are easily rubbed off. The 
antennae are long, sometimes very long, and 
usually with a whorl of hairs on each seg¬ 
ment (Fig. 521); the legs are slender and 
quite long, but the coxae are not greatly 
elongate, and the tibiae are without spurs ; 
the wing-veins (Fig. 522) are greatly reduced 
in number; the anal veins being entirely 
wanting, and vein V wanting or merely 
represented by a slight, unbranched fold. 
To this family belong the smallest of 
Ftg. 521.—Antennas 
of gall-gnats. w, 
male ; f. female, 
enlarged more than ..... J 
that of the male. the midge-like flies. On account of their 
minute size, the adult flies are not apt to attract the at¬ 
tention of the young student. But the larvae of many 
Tom* 
Fig. 522.—Wing of gall-gnat. 
species cause the growth of galls on plants; some of which 
are sure to be found by any close observer. Other species 
arrest the growth of the plants they infest, and thus cause 
