MR. NEWPORT ON THE TEMPERATURE OF INSECTS. 
285 
Melolontha solstitialis, Steph. 
June 26, 1834, a.m. — The specimens employed on the present occasion were cap- 
tured on the evening 1 of the 25th, the temperature of the atmosphere being 70°*5 ; a 
single specimen, which had been lying for some time at rest, had a temperature only 
of /0°'8. Five specimens which had previously been very active, and were now per- 
spiring profusely, raised the temperature of a phial, whose cubic bulk was about two 
inches, from70 o- 5 to 71°‘4. Nine insects in a similar-sized phial raised the tempera- 
ture in four minutes from 70 o, 5 to 72°*2, and a few minutes afterwards to 73 0, 2. During 
this time the insects were in a state of the greatest excitement. The bulb of the ther- 
mometer was not brought into contact with the bodies of the insects. When the 
thermometer was placed among the beetles, and in contact with their bodies, the 
mercury rose to 74°*5, a difference of at least 4° above the original temperature of 
the bottle ; but this was far from being the full amount of the heat of these insects. 
During these observations I found that a large amount of heat generated by the in- 
sects confined in the phial becomes latent, and also that much caloric is radiated 
from the exterior of the phial, which becomes heated by the beetles and warm air 
within, as is proved by the fact that when the thermometer is held very close to the 
side of the phial without touching it, the mercury is considerably affected, and when 
the bulb of the thermometer is held in contact with the phial the mercury ascends 
the scale. In the present experiment it rose more than a degree when the bulb of 
the thermometer touched the side of the phial. It must not be forgotten that besides 
this difficulty in our observations on the temperature of insects, there is another which 
prevents us from knowing the exact amount of heat generated by the insect under 
examination. It is seen in these observations on the Melolonthce, as before shown in 
the Bombi, that a large amount of the heat generated by the body of an insect quickly 
.passes off into the surrounding medium. But if the excited state of the insect be ex- 
cessive, and the consequent evolution of heat greatly exceed its usual amount, nature 
has resorted to another expedient for cooling down the animal body, through means 
of a profuse perspiration, which is carried on in insects perhaps to a greater extent 
than in other animals. Thence the amount of heat believed to be generated under 
certain conditions is only comparative ; but when, as in experiments made on many 
specimens collected together, a profuse perspiration breaks out among the insects, 
the amount of temperature indicated by the thermometer introduced among them is 
much lower than the real amount that has been produced. This was the case in the 
present instance : the specimens were in a state of profuse perspiration, besides which 
they had fasted about eighteen hours. These facts were further illustrated by a sub- 
sequent experiment, in which eighteen specimens were employed in the same sized 
phial ; they were crowded together, and allowed to remain about a quarter of an 
hour in a state of great activity, until they became gradually weakened, were bathed 
with perspiration, and were becoming quiet and asphyxiated with the carbonic acid 
2 p 2 
