264 
MR. NEWPORT ON THE TEMPERATURE OF INSECTS, 
I. Temperature of the different States of Insects. 
1 . The Larva. 
The temperature of the larva is always lower than that of the perfect insect of the 
same species, provided both individuals be in a similar state of activity relative to 
their usual condition. This circumstance must never be neglected when making 
comparative observations on the different states of the same insect. Thus the larva 
of the more perfect hyinenopterous insects, the common Humble Bees, Bomhi, An- 
thophores, Eucerce, &c., which in all their stages have a temperature higher than 
perhaps any other insects, in their active larva state vary from about 2° to 4° Fahr. 
above the temperature of the surrounding medium, while the same individuals in their 
perfect state, when moderately active, have a temperature of from 3° to 8° or 10° Fahr. 
higher than that medium ; but when the same insect is very greatly excited the 
amount of difference is raised to a much greater extent. There is a similar difference 
between the temperature of the larva of the common Flesh Fly, Musca vomitoria, Linn. 
and that of its perfect insect, only that the amount is not so great as in the hyme- 
nopterous insects. In the Musca the amount of temperature in the larva state seldom 
exceeds l a 5, and in the perfect perhaps not more than 2°*5, above that of the sur- 
rounding medium. It is probable that this estimate of the difference between the 
larva and perfect state of dipterous insects may be rather too little, owing to the 
difficulty of making observations on these insects individually, their small size ren- 
dering precision in the experiment almost impossible. But the fact is sufficiently 
clear that they have not so high a temperature as hyinenopterous insects. The same 
difficulty does not exist in making observations on large insects, particularly on the 
large soft-bodied larvae of the Sphinges, and accordingly it is found that in these lepi- 
dopterous insects we are better enabled to ascertain the maximum amount of heat 
evolved by the larva, and the difference which exists between its powers of generating 
heat and that of its perfect insect. This difference is greater in lepidopterous insects 
than in dipterous, and approaches nearer to the hyinenopterous. It was in the larvae 
of lepidopterous insects that I first observed the existence, and the varying amount 
of temperature in individual insects. These observations were commenced in Sep- 
tember 1832. At 24 p.m. September 14, the temperature of the atmosphere being 
62°5 Fahr., the bulb of a thermometer was applied to the under surface of the body 
of a full-grown larva of Sphinx Atropos , Linn., which had discontinued feeding pre- 
paratory to undergoing its transformation. The insect then weighed 365|- grains. 
Previously to the observation it had been for a considerable time in a state of violent 
excitement, and was moving about with great rapidity. Its temperature, as indi- 
cated by the thermometer, was then 70° Fahr., or 7°’5 higher than that of the atmo- 
sphere. This, however, was much higher than its real temperature, which is probably 
not more than 3°, and was occasioned, as I subsequently had reason to believe, by 
