1915] 
Muttkowski: New Insect Life Histories 
111 
and irregular, and often absent from the posterior annuli. Prothorax 
in the posterior annulus each side with a prominent respiratory tubercle, 
which is black in the distal half, clear proximally. Two annuli are present 
in each segment of the thorax, each provided with a pair of chitinized 
brown plate on the posterior part’ of each annulus. 
Abdomen with the first segment showing only two annuli, the following 
six segments each with three annuli. Each of the annuli shows a chitinous 
dorsal plate in the posterior part, elongated transversely, so that twenty 
plates are found on the abdomen of the larva. The plates increase in 
size posteriorly, are very large on segment seven, while comparatively 
small on the first three abdominal segments. These plates vary in size 
and are always present although they may be quite small and barely in- 
dicated on the median segments. This chitinization is found in all of 
the larvae, including such that measure barely 3 mm. In the three pos- 
terior segments there is an indication of grouping of plates by threes so 
that the abdominal segments may be thereby recognized; this grouping 
is obscure on the median segments and it is often very difficult to say 
where a segment leaves off. Each segment at the side bears a few setae 
on a slight protuberance of the segment. 
The last segment is as long as the seventh, entirely chitinous, taper- 
ing evenly, with a basal swelling. The segment is furcate dorsally and 
ventrally, each furca ending in a tubercle equipped with a fan of bristles. 
Ventrally, at the base of the last segment, can be seen the anal papilla, 
divided into four lobes. The prominence of this papilla suggests a second- 
ary use for purposes of locomotion. Such a use was determined experi- 
mentally; the larva uses it much in the looping fashion of the span-worm 
0 Geometridae-Lepidoptera ) pushing itself forward while contracting and 
slightly lifting the middle body segments. 
The larvae were present in great quantities, in all stages from 
egg to pupation. However, the great majority were of one 
size, indicating an obscure periodicity which is also present in 
the adult. 
The larva is distinct from all other Psychodid larvae (thus 
far known) by the extent of chitinization reached in this form. 
For the sake of convenience a key compiled from the literature 
is reproduced. 
Table of the known North American Psychodid larvae 
A. Larvae dark, chiefly aquatic (some semi-aquatic or from moist re- 
gions). Last segment oblong, not tapering, 4 terminal fans of 
bristles. Each body segment with annular dorsal chitinizations, 
each plate with lateral seta. Ventral chitinous plates, present on 
most segments. Pericoma 
a. Larva stout, compressed, equipped with ventral sucking disks for 
attachment Pericoma calif ornica Kincaid 
