266 
MR. NEWPORT ON THE TEMPERATURE OF INSECTS. 
in the same insect, but varies according to certain conditions of the insect. These 
views were still further confirmed and extended by observations on the Sphinx li- 
gustri, S. populi, S. ocellata , Linn., and Cerura vinula, Steph. The first and last of 
these insects, from their large size and frequency of occurrence, afford us the means 
of ascertaining all the facts connected with the temperature of larvae, and are those 
on which most of my subsequent observations have been made. It is at about the 
fifth or sixth day after the larva of Sphinx Ugustri has assumed its last skin, that it 
evolves the greatest quantity of heat. It then feeds most voraciously, and usually 
weighs about 80 grains. Its greatest temperature is then 1°*3 above the temperature 
of the atmosphere. I have seldom or ever found it higher, while on the eighth or 
ninth day it seldom exceeds nine tenths, and a little while before its change into the 
pupa state perhaps not more than five tenths. Its quantity of respiration at that time 
is diminished, and its temperature is reduced by copious cutaneous perspiration, 
which becomes very apparent when the insect is much excited. The difference which 
exists in the maximum amount of heat generated by the larvse of different species of 
the same class of insects, appears to have some reference to the habits of those species. 
The greatest amount, so far as I have yet ascertained, excepting only the Sphinx 
Airopos before noticed, appears to be generated by the larva of the Puss Moth, Cerura 
vinula, Steph., which usually lives on the boughs of trees, and subsequently undergoes 
its changes on the trunk or limbs of the tree a few feet from the ground, has a higher 
temperature of body, and a quicker circulation of its fluids than the larva of the 
Sphinx, which undergoes its changes in the earth. The larva of the Cerura in its 
most active condition sometimes has a temperature of l 0, 8, or nearly half a degree 
higher than the Sphinx ; but I have not observed the same difference between the 
temperatures of the perfect insects of these species, both of which constantly reside 
in the open air. The amount of difference between the perfect insect and larva in 
these species, like that of the hyinenopterous insects, is very great. A perfectly 
healthy specimen of Sphinx Ugustri in its perfect condition after violent exertion, has 
sometimes a temperature of nearly 8° above that of its larva. The usual difference is 
about 5°, and the same is the case with the Cerura. 
When the internal temperature of a larva of the Sphinx or Cerura is taken, it is 
found to vary from • 5 of a degree to 1° above that of the external. But all observa- 
tions on the internal temperature of larvse, more particularly of soft-bodied larvse, 
are necessarily uncertain, on account of the reasons before stated. Still it is some- 
times desirable to ascertain its amount, particularly when the specimens have been 
kept in a steady medium. When the internal temperature of the larva of Anthophora 
retusa, Steph. is taken with the necessary care, it is found to be nearly or quite a 
degree above that of the exterior ; but the difficulty in making correct observations 
on these larvse is exceedingly great, owing to the rapidity with which they part with 
their natural heat when exposed to a varying medium. Hence when the observations 
are attempted to be made, even with regard to external temperature, in the natural 
