214 
Parasites of Mosquito Larvae 
It is possible that the softening of the tissues consequent on the death of 
the larva may be necessary in some instances before the organisms, especially 
those in the tougher regions of the body, can make their escape. But escape 
does take place mainly from the larva, while yet alive, either by the rupture, 
or by the complete separation of the gills; for, on looking through a series of 
sickly larvae, it was noticed that often one, sometimes two and rarely all the 
gills were absent; and by placing larvae having the full complement of gills 
but showing infection, each in small separate bowls, the facts as to rupture 
and separation of the gills were verified. 
Larvae did not seem to be greatly affected by the loss of one gill, and 
occasionally specimens which had lost all four were observed. None were ever 
known to pupate, though one larva without any gills managed almost com¬ 
pletely to detach most of its skin in attempted pupation, then dying with the 
skin still enveloping its last two or three segments. 
On the death of the last larva a fresh batch of fifty half-grown Stegomyia 
larvae were put into the water; most of these pupated and a few died, but 
showed no evidence cf the presence of the protozoa. Thereafter until October 16, 
almost three months later, batches of the larvae were from time to time put in, 
keeping the number constantly between thirty and fifty, a little of the fluid 
in which they had occurred being added to make up for the evaporation of the 
original water. 
During all these weeks there was a constant succession of pupations or 
deaths among the larvae and it was not until this date that the protozoa again 
showed evidences of their presence. It is perhaps noteworthy that during the 
last fortnight the bowl, which had been kept in a well-lighted situation, had 
been removed to a dark corner of the laboratory. 
On October 16 three of the larvae, floating at the surface, were seen each 
with one milky-looking gill in which, on microscopic examination, the protozoa 
were found to be swarming, the other three gills being affected to a less degree. 
An examination was then made of every larva and out of twenty-seven, 
thirteen were apparently healthy, while fourteen, some lacking one or more 
gills, showed the presence of the parasites to a greater or less extent. 
The appearances presented by each of the affected larvae, most of which 
were approaching maturity, were as follows, the specimens being numbered 
1-14: 
(1) Alive; one gill showing extreme distension with organisms; one gill 
about half-full; other gills showing one organism each: very moderate body 
infestation, a few only here and there.—(2) and (3) As specimen (1).—(4) Dead: 
had lost one gill. In one of the remaining gills were about twenty of the 
parasites, spherical, immobile and apparently attached to each other, for they 
moved en masse when some of the living organisms, of which there were about 
ten, butted against them. In each of the other two gills were about an equal 
number of resting and actively moving organisms, about twenty in all. These 
teemed in the body.—(5) Alive; had lost two gills. The remaining gills showed 
