428 
THE STUDY OF INSECTS. 
opening, which is formed by a lengthwise split on the back 
near the head-end and a crosswise split at the front end of 
this (Fig. 498). In a few members 
of this suborder (i.e., some of the 
Cecidomyiidai) the pupa escapes 
through a crosswise split between 
the seventh and eighth abdominal segments. The pupae 
are usually either naked or enclosed in the last larval skin, 
the puparium; but the pupae of some of the gall-gnats, 
Cecidomyiidae, are enclosed in cocoons. The adult flies do 
not possess a frontal lunule. Sec footnote page 416. 
Family Psychodid^e (Psy-chod'i-dae). 
The Moth-like Flies. 
There may be found frequently upon windows and on 
the lower surface of the foliage of trees small flies which 
have the body and wings densely clothed with >/ 
hair and which resemble tiny moths in appear- 
ance. The wings are broad, and when at rest 
slope at the sides in a roof-like manner or are 
held horizontally in such a way as to give the Flc 499 ._ A 
insect a triangular outline (Fig. 499). motii-iikc fly. 
The moth-like appearance of these insects is sufficient to 
distinguish them from all other flies. The venation of the 
m 4 
nil* 
Vila 
Fig. 500.—Wing of a moth-like fly. 
