330 
THE STUDY OF INSECTS . 
as long as the body; but in one subfamily it is short and 
membranous. When not in use it is closely coiled like a 
watch-spring beneath the head. None of the species have 
ocelli. 
The venation of the wings (Fig. 407) is quite character¬ 
istic ; the most distinctive feature is the presence of what 
Fig. 407.—Wings of Phlegethontius celeus. 
appears to be a cross-vein between subcosta and radius ol 
the hind wing. This apparent cross-vein is due to the fact 
that veins II and III are grown together for a short distance, 
and then vein II separates and joins vein I. The obvious 
presence of vein I in the hind wings is unusual; but it occurs 
in the Psychidae, in the Bombycidae, and in the Anthroceridae 
(a family not represented in our fauna) also. This basal part 
of vein I is probably preserved in other cases where it appears 
to be the base of vein II. Thus in Citheronia (Fig. 417) there 
:s a rudiment of the so-called cross-vein, which has entirely 
disappeared in the more specialized forms of the family to 
