484 
Stegomyia fasciata 
A few rough experiments in which masses of bacteria and yeasts 
scraped from the surface of agar cultures were dropped into water 
containing larvae, showed that the larvae congregated round and 
greedily devoured them. Their jaws were evidently used to tear and 
disrupt the clumps of organisms, while the turbid cloud which formed 
round the struggling crowd of larvae was rapidly dissipated, presum¬ 
ably by the sweeping action of their mouth brushes. 
Before describing the experiments and discussing their results, some 
preliminary explanations are necessary. For the sake of those readers 
who have no practical knowledge of mosquito breeding it is necessary 
to state that the conditions favourable for rearing the adults, though 
simple, require some nicety of adjustment for success, when the breed¬ 
ing pans are small. The essential points are temperature, the amount 
of nutriment in relation to the quantity of water, and the number of 
larvae in relation to both the latter factors. The temperature through¬ 
out the experiments under sterile conditions was 75° F. which if not 
quite high enough to give the speediest passage from egg to adult, is 
quite favourable for the species. 
The amount of nutriment and number of larvae in proporticm tc 
the quantity of water were, however, in some of our experiments highly 
artificial. 
In Bacot’s report (1916) referred to above, the adjustment of these 
factors is dealt with from the aspect of the rearing of healthy adults. 
With the present research such careful adjustment was often neither 
possible nor necessary, the actual number of adults reared being alto¬ 
gether of secondary importance to the hatching of dormant eggs, and 
the relative speed of larval growth. Healthy conditions for the larvae 
occur when they are able to hold bacterial multiplication in check, when 
they do this very thoroughly their progress is slow and steady, if they 
hold it slightly in check their development is more rapid, while in 
cases where tbe balance of forces is delicate, larval growth is apt to be 
very rapid, resulting in a life or death race between them and the growth 
of bacteria. It mattered but very little if this balance, which could not 
in many cases be readily foreseen, resulted in the destruction of the 
larvae before the completion of their development owing to the exuber¬ 
ance of bacterial growth. While, although the lagging or eventual 
starvation of the larvae from lack of sufficient nourishment in some of 
the more narrowly adjusted experiments is regrettable, it need not lead 
to any confusion so long as it is borne in mind that the comparison of 
speed in growth must be made between the larvae in tubes of the same 
