E. E. Atkin and A. Bacot 
501 
Our conclusion respecting the evidence as a whole may be stated as 
follows: that the larvae of Siegomyia fasciata greedily consume both 
bacteria and yeasts on which they can thrive in the absence of any 
other food, whereas in very many instances they fail entirely to develop 
on a variety of nutritive fluids and particles, including dead bacteria, 
under sterile conditions. In the far less numerous cases where progress 
was made under apparently sterile conditions, growth was always 
relatively very .slow' to that under otherwise equivalent but unsterile 
conditions, and the mortality w'as very high. The rearing of adults 
under sterile conditions being so exceptional we feel justified in stating 
that the presence of bacteria or yeasts is a practical necessity for the 
maintaining of the species. If one considers the facts shown by Bacot 
(1916) regarding the scarcity of bacteria in the alimentary canal of 
larvae taken from water swarming w'ith bacteria in relation to the 
exclusively browsing habit of the young larvae and its partial retention 
by the older ones when feeding, together w'ith the experimental results 
above recorded, there seems good reason for supposing that bacteria 
and yeasts afford the chief food supply of the larvae. The ingestion 
of larger particles and the structure of the jaw's are not incompatible 
with this view, because such particles are likely to be covered wdth a 
bacterial growdh w'hile the jaws are of use in gnawing away portions of 
decaying organic matter. They w'ere evidently used to disrupt clots of 
both bacteria and yeasts in the preliminary experiments mentioned in 
the introduction. 
It seems probable that this knowledge may be of assistance in the 
destruction of this species of mosquito, as it should enable the methods 
now so largely available for the purification of water from bacteria to 
be utilized. On a minor issue it may be of service in enabling Sanitary 
Officers to escape the annoyance caused by the failure to breed more 
than one or two isolated species from jars containing mosquito larvae 
captured by their inspectors. This failure no doubt arises owing to 
starvation, because the bacteria are killed by the action of light, it 
being customary to stand jars with wrigglers in the full light of a window. 
There is the further possibility that the eggs after a careful and probably 
lengthy research might be found to be of service as a rough and ready 
means of testing the relative purity of water in regard to living 
organisms. 
33—2 
