INTRODUCTION. 
Besides the external gills many trichopterous larve possess anal 
gills, which are located within the anus and are capable of protru- 
sion. In preserved specimens they are usually completely con- 
cealed within the cavity of the body, for which reason they offer 
unsatisfactory taxonomic characters. Even the external gills are 
not altogether reliable for taxonomic purposes, except in their gen- 
eral grouping ; for tufts of gills often contain different numbers of 
filaments in different individuals of a species, or even on opposite 
sides of the same individual. Also, especially on the more caudal 
gill-bearing segments, the gills on some specimens are very feeble, 
or drop out entirely, while on other specimens they are well repre- 
sented. However, the same type of gills is always found in the 
same species, and the gills that are present always arise from the 
same parts of the segments. 
The terminal abdominal segment bears a pair of more or less 
fleshy prolegs, each of which terminates in a movable chitinous 
hook. In some of the case-making larve the bases of the prolegs 
are fused, forming an apparent tenth segment, while in other spe- 
cies they are separate, apparently arising from the ninth abdominal 
segment. Ulmer considers ten segments usually present, but the 
weight of evidence points to but nine segments, the apparent 
tenth being but the fused bases of the prolegs. 
DESCRIPTION OF THE Pupa’.—lIn external appearance Trichop- 
terous pupe have many of the characters of the adults. Their 
legs, antennz, and wing-pads are free from the body, and their 
general form is much the same as that of the perfect insect. 
The head is formed much like that of the adult. In those 
forms that have antenne shorter than the body, the antennez are 
straight and are laid close along the sides of the pupe. In forms 
with antennz much longer than the length of the body they project 
backward along the sides of the insect until nearly reaching the 
end of the abdomen, when they turn abruptly and entwine round 
and round its caudal segments. The labrum is very different 
from that of either larva or adult. It is armed with several 
very long spines which probably serve to keep the mesh of 
the pupal case free from silt. These spines have characteristic 
form and grouping in different species. The mandibles are long 
and heavily chitinized, usually possessing several sharp teeth. It 
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