288 MOSQUITOES OF NORTH AMERICA 
these different kinds of water were not ordinarily very marked. They decided, 
however, that the vigor and the strength and the size of the perfect insect which 
resulted was in distinct relation with the larval food. Reed and Carroll found 
that muddy water is unfavorable to the larve. “In water, however, which con- 
tains much suspended soil—muddy water—the larve, in our experience, do not 
flourish, but die off rather rapidly.” 
DURATION OF EARLY STAGES. 
Temperature has the greatest influence, not only upon the hatching of the 
eggs, but also upon the subsequent development of the larve. The effects of 
various temperatures on the early stages of calopus were carefully investigated 
by the American commission in Cuba and by the French commission at Rio de 
Janeiro and the results of both agree very closely. 
The shortest period of development to imago observed by Reed and Carroll 
during summer weather in Cuba was 94 days, divided as follows: incubation 2 
days; larval stage 6 days; pupal stage 36 hours; but they believed that this was 
quite exceptional. Their observations on the influence of temperature on de- 
velopment are as follows: 
“ We have just seen that at summer temperatures the time required for a com- 
plete generation of this insect is from eleven to eighteen days. We may say that 
at an average temperature of 75° F., or over, stegomyia multiplies abundantly. 
Exposure to a cooler temperature, even for a short time daily, much retards the 
development of this mosquito. Thus, a batch of fifty-one eggs kept at 35° C., 
but which were placed in a cool chamber at 20° C. for two hours daily during the 
whole process of development, although furnishing a few larve at the end of the 
third day, were not all hatched until the eleventh day. The first pups appeared 
on the fourteenth day and the first mosquito on the nineteenth day; the whole 
process being completed in twenty-seven days, instead of the usual fifteen or 
eighteen days. The loss of insects was about 50 per cent. Eggs kept at a tem- 
perature of 20° C. (68° F.) do not hatch, in our experience. Newly hatched 
larve kept at this temperature develop very slowly and require about twenty 
days to reach the pupal stage. Mosquitos developed under such conditions are 
feeble, and but few arrive at maturity. Young larve kept at 10° C. (50° F.) 
have failed to reach the pupal stage—although some growth takes place. In one 
experiment more than 50 per cent, were dead at the end of two weeks, and none 
survived the thirty-second day. Half grown larve and pup exposed to a tem- 
perature of 20° C., and even as low as 10° C., continue to develop slowly, but the 
few insects which escape drowning have, as a rule, been of feeble strength and 
have refused to bite. Although the reduction of the temperature to the freezing 
point, or below, would not necessarily destroy the vitality of the eggs of this 
genus of mosquito, it should be remembered that a reduction of temperature to 
68° F., or below, for even a few hours of the twenty-four, will much retard the 
development of the generation. Ata temperature less than 68° F. the eggs of 
this insect have ceased to hatch.” 
Under the most favorable conditions of food and temperature the larva de- 
velops with great rapidity. When the conditions are very unfavorable larval 
life may be prolonged indefinitely, the larve showing great resistance. Agra- 
monte places the minimum period of development from egg to imago at ten 
