AEDES CALOPUS AND TEMPERATURE 271 
days and that even when allowed to suck blood they will still die in a few days 
if deprived of water. 
INFLUENCE. OF TEMPERATURE. 
The French investigators pointed out that one of the most striking character- 
istics of calopus is its extreme sensibility to differences in temperature and this 
has been confirmed by many observations. They were impressed by the great 
activity which the insect showed when the thermometer ranged in the vicinity 
of 28° Centigrade (82° Fahrenheit), the temperature at which it displayed the 
greatest energy. In contrast with this was the markedly reduced activity when 
the temperature rose or fell a few degrees above or below that point. Beyond 
39° C. (102° F.) the heat is fatal to it. If the thermometer goes below 15° or 
16° C. (59° or 61° F.) it becomes sluggish and will not feed. At 12° to 14° C. 
(54° to 57° F.) it becomes torpid, flies with difficulty and no longer stands 
firmly on its legs. At temperatures of from 14° to 18° C. (57° to 64° F.) 
calopus not only does not bite in freedom but refuses to bite when put in a glass: 
tube and placed in contact with the skin. Only when the temperature inside the 
tube is raised sufficiently by the heat of the hand does the mosquito bite. Ata 
temperature of 14° C. twelve mosquitoes in tubes were placed in contact with 
the arm and kept there for 15 minutes without showing any willingness to bite. 
At 17° C. the result was the same. At 18° C. nine of these same mosquitoes bit, 
one after five minutes, the remainder after seven and eight minutes. These in- 
vestigators do not believe that in nature calopus will bite below 17° C.; they 
found that it would bite readily between 22° and 25° C. (72° and 77° F.) but 
that the temperature which suits it best is between 27° and 30° C. (81°-86° 
F.). Reed and Carroll made some interesting observations on the effect of tem- 
perature on biting with the yellow-fever mosquito. They may be quoted as 
follows: 
“ As regards the effect of temperature on the stinging of stegomyia fasciata, 
the results of a number of observations made by us show that this mosquito will 
bite at temperatures of 62° F. and above. At temperatures below this point, we 
have not, as yet, succeeded in inducing even very hungry females to suck blood. 
We may, therefore, say that observations thus far made appear to show that 
stegomyia fasciata, while not breeding at temperatures below 68° F., will still 
bite at a temperature as low as 62° F., but probably not at lower temperatures. 
“Tf this insect is concerned in the propagation of yellow fever, it is now quite 
apparent why an epidemic of this disease should fall to a low ebb in the city of 
New Orleans during the month of November, with a mean temperature of 
61.8° F., and practically cease in December, with a mean temperature of 55.3° 
F. Acareful study of the charts herewith submitted, showing the monthly mean 
temperatures of the cities of Havana and New Orleans and Havana and Rio de 
Janeiro, together with the relative monthly mortality from yellow fever in these 
cities, will prove of interest, we think, as showing better than laboratory ob- 
servations the general effect of temperature upon the breeding and biting of 
stegomyia fasciata. In the light of recent researches, we can now understand 
that while yellow fever can, and does, prevail during the entire year in Havana 
and Rio de Janeiro—although at a comparatively low ebb during the winter 
months—it cannot propagate itself in New Orleans from December to May.” 
