SCIENTIFIC SURVEY OF TURNER'S LAKE 23 
A CADDISFLY GUEST OF THE FRESH-WATER 
SPONGE 
BY SHERMAN C. BISHOP 
Some fragments of a fresh-water sponge* collected in September 
1922 in Turner’s lake, Isle-au-Haut, Maine, and preserved both in 
alcohol and by drying, were found on examination to contain a 
considerable number of the larvae and cases of an interesting micro- 
caddisfly. Some of the cases were wholly enveloped in the sponge 
tissue, others only partly overgrown, while a few individuals 
retained their hold on independence by moving about often enough 
to prevent permanent attachment. 
In the construction of the case a silk foundation is used but the 
external protective material is composed of the transparent 
sponge spicules laid first in more or less regular transverse rows 
then apparently stuck on haphazardly or perhaps simply 
entangled on the surface. The cases are minute, slightly curved 
and tapering cylinders varying from 2 to 5 or 6 mm in length 
and greenish in freshly collected material but turning to light 
brown in preserved specimens. The smaller end, in perfect 
cases, is sharply constricted and usually free from spicules; the 
anterior end has a slightly projecting hood (pl. 1, fig. 2.) Only a 
single case was observed that had served as a pupal chamber and 
this was provided at each end with a net work of fine silk sup- 
porting heavier rings of the same material (pl. 1, fig. 3). The 
insect had escaped by cutting away the silken barrier until it hung 
on one side like the lid of a coffee pot. 
The larva (pl. 1, fig. 1) itself is slender and almost transparent 
and lacks the abdominal respiratory filaments; the legs are 
progressively longer and slimmer from before backwards. The 
first legs are decidedly heavier than the others and have the 
femora provided with serrated ridges bordered on each side by 
stout spines (pl. 1, fig. 4); the tibiae are widened distally and each 
armed with a single blunt spine and a few hairs; the tarsi, like 
the femora, bear serrated ridges which may be opposed to those 
of the femora to form effective grasping organs. The second and 
third pairs (pl. 1, figs. 5-6) are long enough to extend to the front 
of the head or beyond and bear many slender spines or hairs 
*1. The sponge has been identified by Prof. Frank Smith as_ probably 
Heteromeyema ryderi Potts; positive determination is impossible owing to the 
lack of gemmules in the young colonies. 
