MR. NEWPORT ON THE TEMPERATURE OF INSECTS. 
265 
holding the insect in my hand while making the observation. At 12^ midnight, at- 
mosphere 60 o, 5, the larva perfectly at rest had a temperature of only 61° Fahr. ; and 
at 7 o’clock on the following morning, September 15, having remained perfectly quiet 
and apparently asleep since the last observation, the temperature of the atmosphere 
continuing at 60 o- 5 Fahr., when the bulb of the thermometer was gently pressed 
against its side without disturbing it, and allowed to remain there for a quarter of 
an hour, the mercury was not perceptibly affected, the temperature of the larva, now 
in a complete state of rest, being exactly that of the surrounding atmosphere. Ob- 
servations in every respect similar to these were also made at the same time on the 
larva of the Bull-headed Moth, Pygcera bucephala , Steph. At midnight the tem- 
perature of the atmosphere, as before stated, being 60 o, 5, the thermometer was ap- 
plied to the under surface of a larva that had been lying perfectly at rest for several 
hours, and although it now became slightly aroused its temperature was only 61° Fahr. 
At 7 on the morning of the 15th, the larva still perfectly quiet, and the thermometer 
placed in contact with it, and, as with the Sphinx Atropos, allowed to remain for a 
quarter of an hour, there was no indication of any increase of temperature, the tem- 
perature of the insect being exactly that of the atmosphere ; but a few hours after- 
wards, when the thermometer was again applied to the same insect, which had be- 
come slightly active, the mercury rose to 60°*5, the temperature of the atmosphere 
being then 60° Fahr. At 6^ on the morning of the 17th the observations on this 
species were repeated. The temperature of the atmosphere was then 62° Fahr. ; and 
when the bulb of the thermometer was applied to a full-grown larva, which had been 
remaining several hours at rest, the mercury rose very nearly to 63° Fahr. The ob- 
servation was then repeated on several other individuals of the same species, which 
had been lying at rest, and with precisely similar results. The bulb of the thermo- 
meter was then placed in a box which was filled with these larvae, and being com- 
pletely covered with them was suffered to remain for ten minutes, during which time 
they were in a state of great activity, and the mercury rose to 63°’3 Fahr., a differ- 
ence of 1°*3 Fahr. Subsequent observations on the temperature of other species of 
lepidopterous insects confirmed these observations ; and it was remarkable that the 
amount of temperature in the larvae of different tribes of this order is pretty nearly 
the same. On the 26th of June 1834 I examined the full-grown larva of Pavonia 
minor , which like the preceding species had been at rest for several hours, and found 
that the temperature of the atmosphere being 68°, the temperature of the insect was 
only 68 0, 3. The insect then became a little excited, and the mercury rose to 68 0, 7 ; 
and when still further excited to 68 0, 9, and ultimately to 69°‘3, being a difference of 
1 0, 3 above that of the atmosphere, thus proving that the temperature of an insect in- 
creases immediately it becomes active, and that the increase is in proportion to the 
degree of activity, and probably also to the quantity of respiration of the insect. 
From these facts it is sufficiently clear that individual insects possess a temperature 
of body above that of the surrounding medium, and that the amount is not constant 
