FISHES IN RELATION TO MOSQUITO CONTROL. 5 
there is not much vegetation, but considerable wave action, and as a 
rule these ponds are not well suited to prolific mosquito breeding. 
GAMBUSIA AFFINIS AND THE GENERAL PLAN PURSUED IN TESTING 
ITS VALUE IN ANTIMOSQUITO WORK. 
Gambusia was selected for the present tests because, first, it seeks 
its food at the surface, which appears to make it especially suitable 
for antimosquito work; second, it lives and thrives under a large 
variety of conditions and especially in water suitable for the support 
of mosquito larve; third, it proved to be quite common in the extra- 
cantonment zone and adjacent territory; fourth, it is very prolific; 
and fifth, its usefulness in destroying mosquito larve in aquaria 
and fountains was already well known. 
This fish does not lay eggs, but gives birth to well developed and 
very active young. It, therefore, requires no special environment, 
as most other fishes do, for depositing and hatching the eggs. Young 
Gambusia affinis (female). 
of the season were noticed for the first time on April 24, and during 
the latter half of October a gravid female still occasionally appeared 
among collections. The author,? working with Gambusia at Beau- 
fort, N. C., found that it breeds throughout the summer and that a 
new brood is produced at intervals of about one month or six weeks. 
It was observed that a single female gave birth to six broods of 
young during a single season. The number of young produced at 
one time appears to bear a direct relation to the size of the female, a 
large female producing many more young than a small one. The 
largest brood observed by the writer numbered 63, but Smith, 
working with fish from the Potomac River, found 100 in a single brood. 
The young are approximately one-half inch in total length when 
born; they are very active and are apparently much better adapted 
to begin the struggle for an existence than most fish hatched Hee 
eggs. They, in fact, are ready to begin the work of destroying 
mosquito larve at once, for the writer has seen them attacking and 
eating small and even medium-sized mosquito larve in aquaria 
before they were a day old. Gambusia gains growth rapidly and 
the earliest broods of the season, born in April and May, become 
a Hildebrand, Samuel F., Report, U. S. Commissioner of Fisheries, Appendix VI, 1917, p. 6. 
> Smith, H, M., Science, n.s., Vol. XXXVI, 1912, p. 224, 
