274 
MR. NEWPORT ON THE TEMPERATURE OF INSECTS. 
their dwelling, as I shall presently have an opportunity of proving. The common 
Humble Bee, Bombus terrestris, even in the month of April, will continue in a state 
of rest # approaching to the condition of hybernation for at least twenty hours, while 
its temperature becomes diminished in proportion to the diminution of its quantity 
of respiration, which also is diminished in proportion to the length of time it remains 
in a state of rest. This is always the case with insects when the temperature of the 
surrounding atmosphere is stationary. But if the temperature of the atmosphere is 
gradually increasing when an insect is passing into a state of repose, the temperature 
of the insect will continue to rise also, accompanying that of the atmosphere, but not 
so rapidly as it would have done were the insect in a state of activity, so that the 
temperature of the air and of the insect will at length arrive at exactly the same level; 
and if, when this is the case, the temperature of the atmosphere continues rising, that 
of the insect will also accompany it for a certain time ; but if the increase of atmo- 
spheric temperature be very rapid, the temperature of the insect will at length be 
found to be one or two tenths of a degree below that of the atmosphere. When this 
has happened the insect generally becomes slightly aroused, fetches one or two deep 
inspirations, and its temperature very quickly rises to that of the atmosphere, while 
the insect relapses again into its previous slumber. On the other hand, if the tempe- 
rature of the atmosphere be gradually diminishing, that of the insect will also con- 
tinue to be diminished, but will remain for a longer period higher than that of the 
atmosphere when the atmosphere is rising, or is remaining stationary, since the in- 
sect during sleep can neither acquire nor part with its heat so rapidly as the atmo- 
sphere around it. But if the temperature of the atmosphere continues to subside 
rapidly, the temperature of the insect during the whole period of its most profound 
sleep may continue considerably higher than that of the surrounding medium. These 
facts may be readily demonstrated by careful observations on the smooth-bodied 
larvee of Lepidoptera, the best of which for this purpose are the larvae of the Sphinges, 
in which besides the varying amount of temperature, the correspondent rate of pul- 
sation may also be observed with great accuracy. The larva of Sphinx ligustri upon 
which the observations detailed in Table No. II. were made, had arrived at the 
seventh day of its age after assuming its last skin, or at about the thirtieth day 
after coming from the egg, and consequently was nearly full grown, and beginning 
to feed rather less voraciously than on the two preceding days. At the time my ob- 
servations were commenced it had been lying at rest about an hour, having fed plen- 
tifully in the morning. The whole period of observation, throughout which it was 
sleeping almost uninterruptedly, was about nine hours. During this period the 
thermometer was allowed to remain entirely undisturbed on a table in close contact 
with the ventral surface of the insect, while a second thermometer, with which the 
one employed to take the temperature of the insect had been carefully compared, 
was used to take the temperature of the atmosphere, which throughout the obser- 
* Philosophical Transactions, 1836, Part II., p. 555, Table L, No. 27. 
