

402 THE AMERICAN NATURALIST. [Vor. XXXVI. 
that of the atmosphere, and only begins to approach atmospheric 
temperature just before partial heat paralysis of the wing muscles 
sets in. . After death the temperature of the insect and the air are 
the same. But when the air is very damp the body temperature of 
the insect is higher than that of the air. This is explained as due to 
evaporation of the body fluids and to respiration, the former having 
a tendency to diminish, the latter to raise, the temperature of the 
insect. Bachmetjew predicts that the study of the dependence of the 
body temperature on that of the air, under different conditions of 
moisture, will ultimately enable us to determine the metabolism of 
these animals, and hence their vitality at different temperatures. 
The influence of the activity of the insect on its body temperature, 
long since noted by Newport (1837) and others, is exhaustively 
studied by Bachmetjew. While a moth is moving its wings its body 
temperature keeps rising, but falls suddenly with the cessation of this 
movement. The insect was studied under three conditions : first, at 
the ordinary temperature of the room ; second, at a higher tempera- 
ture in the thermostat ; third, at a lower temperature in a cold-air 
bath. Experiments conducted at room temperature show that the moth 
(Sphingid) is incapable of raising its own temperature higher than 
38.5" C. by means of muscular movement. Fluttering of the wings 
does not produce as high a temperature as “humming.” At about 
38° C. the insect often suddenly changed from humming to fluttering, 
or rested completely. Bachmetjew interprets this change as due to 
partial heat paralysis of the muscles. It is a transitory phenomenon, 
which disappears with the sinking of the temperature during rest to 
that of the surrounding atmosphere. The temperature at which the 
wing muscles are paralyzed (in Deilephila euphorbiz) increases with 
an increase of the temperature (at ordinary moisture) and reaches 
45.5^ C., after which the moth loses the power of humming. Com- 
plete, #2, no longer transitory, heat paralysis of these muscles super- 
venes at a body temperature of 49.77 C. In somewhat moister air 
this result does not set in till 53° C. is reached. Ina single experi- 
ment on Deilephila at low atmospheric temperature the muscle 
paralysis also appeared, but at a lower temperature. At a body tem- 
perature of — 0.5° C. all movements ceased, fluttering began at 12? C., 
and humming not till 20° C. had been reached. It would seem, 
therefore, that the temperature of partial paralysis of the wing mus- 
cles is directly proportional to the body temperature of the insect, as 
is also the case for higher temperatures. According to Bachmetjew, 

these effects of partial paralysis play a great róle in the production 

