a handbook of the mosquitoes of north america - Systematic Catalog ...

72 MOSQUITOES OF NORTH AMERICA
breeding, maintenance, and furnish them a continuing food
suPPlY*
Other natural enemies occur. Recently a tadpole, Ham-
mond’s Spade-foot (Scaphiopus hammon&i) has been shown to
feed on larvae in New Mexico. I have shown that our ordinary
spotted salamander, (Diemyctylus zGridescen.s) is a most vora-
cious devourer of them .* This species is widespread through-
out many sections of North America but we know scarcely any-
thing about rearing it. Undoubtedly much information will be
gained as the study of mosquito biology receives more atten-
tion.
0 ther Methods of Mosquito Reduction
In recent years, much attention has been devoted to the study
of the aquatic conditions which favor or reduce mosquito breed-
ing. It is a common observation that certain ponds, etc., are
favorite breeding grounds while in other similar ponds or
marshes no breeding occurs. Though much work has been
done, no conclusions seem warranted. Certain aquatic plants
as Churn species, Ph3111otria species, and others appear to have
a deterrent effect both on egg deposition and larval develop-
ment. In general it may be said that the presence or absence of
the necessary larval food appears to be the deciding factor. But
what is the necessary larval food ? Many examinations of larval
gut contents have been made; some studies of the plancton in
typical breeding pools versus non-breeding pools have been
carried out; from these, however, no conclusions can be drawn.
As the larvae sweep all available material into their intestinal
tracts, there are no means of deciding what is actually digested
and what is passed out in the wastes. Only by the carefully
planned rearing of larvae on specific foods or organisms can
progress be made. Such work has been started and results
ought to be forthcoming. If by the use of certain aquatic
* Chandler (1918) has also shown that the western newt (Notoph-
thahus torosus), a close relative of D. viridescem, is an efficient
destroyer of mosquito larvae in Oregon.