154 MOSQUITOES OF NORTH AMERICA 
One of their own kind is as likely to fall a prey as any other species and in fact 
the confinement of several of these larve in a narrow compass usually ends in 
the destruction of all of them but one. 
HIBERNATION OF MOSQUITO LARVEE. 
The continuous breeders, such as Anopheles and certain species of Culex, de- 
velop while temperature conditions are favorable. Cold weather puts an end 
to their activities and the larve are destroyed by the freezing over of the water, 
or perhaps even before. However the larve of certain species normally hiber- 
nate. This is the case with the pitcher-plant mosquito, Wyeomyia smithu; 
the larva survive the complete freezing up of the water in the leaves of the plant 
and complete their development the following season. The larva of a few other 
species of the eastern United States hibernate regularly although they do not 
withstand actual freezing; these larve remain dormant at the bottom during 
cold weather. The tree-hole breeders Bancroftia signifer and Megarhinus sep- 
tentrionalis hibernate as larvee and the same is probably true of Celodiazesis 
barberi. Culex melanurus hibernates as mature larva. The larve live in spring- 
holes in swamps or in the woods and the last brood appears very late in the 
season. They remain at the bottom during cold weather, and do not produce the 
imago until the following April or May. 
All the foregoing species, with the exception of Wyeomyia smithi, may be 
said to be rare and the larve are not generally in evidence. The observations of 
Galli-Valerio and Rochaz de Jongh, in Switzerland, show that in Europe the 
larve of certain species of mosquitoes hibernate in great numbers. Thus it 
appears that the larvee of Anopheles bifurcatus hibernate normally, remaining in 
hiding among the leaves of water-cress (Nasturtium officinale) and other 
aquatic plants. In the case of Culiseta annulatus, which was observed in a 
water-barrel in an open field, even pupe continued to appear throughout the 
winter at temperatures but little above freezing. These observers found that 
larvee of Anopheles and Culex (?) survived in the thin layer of water between 
two sheets of ice. These observers also found that the larve of Aédes nemorosus 
occur during the winter in great numbers. On December 2, 1906, they found 
great numbers of these larve: in an ice-covered puddle. This puddle had a depth 
of five centimeters and an area of six square meters and they calculated that it 
contained about 3,750,000 larve. The larve in these puddles did not increase 
in size during the winter; early in April they finally began to grow and trans- 
formed to pupe towards the end of that month. From another observation by 
these investigators it appears that such larve are hatched from eggs in mid- 
winter. Thus they found on January 15, 1902, great numbers of very small 
larve in a puddle thickly covered with ice; this puddle had been dry between 
December 1 and January 1 and had, as the result of warm weather in early 
January, afterward filled with snow-water. This last species, then, may be 
classed with those species of Aédes the larve of which elsewhere appear in the 
snow-water of early spring. 
