MR. NEWPORT ON THE TEMPERATURE OF INSECTS. 
269 
From these observations it is seen that when the pupa was disturbed there was a 
slight evolution of heat ; the amount of this was greatest when the temperature of 
the atmosphere was subsiding. But as it appears reasonable to infer, a priori , that 
the internal temperature of the pupa may be higher than that of the surrounding 
atmosphere, although the thermometer be not perceptibly affected when applied to 
the thick exterior of the puparium, another specimen of the same insect was subjected 
to examination. This specimen had been lying for several weeks on the surface of 
the ground, in the shade, exposed to all the variations of the atmosphere. During 
that period the temperature of the air had seldom been more than a few degrees 
above freezing, while on the three nights immediately preceding the making of this 
observation, on the morning of the 23rd of March, the temperature of the atmosphere 
bad ranged from 2° to 4° Fahr. below 32° Fahr. On the night of the 22nd it was 
from 3° to 4° below that standard. Under these circumstances there appeared to be 
a favourable opportunity of ascertaining the real internal temperature of the pupa. 
Accordingly at a.m., atmosphere perfectly calm, and its temperature 32 0- 6 Fahr., 
and gradually but very slowly rising, an incision was made quickly with a pair of 
scissors through the posterior part of the pupa, which was held for the moment 
between a pair of forceps that had previously been cooled down to the temperature 
of the atmosphere. The fluids of the insect instantly gushed out, and the entire cy- 
lindrical bulb of a small thermometer was immediately passed into the body of the 
pupa. It was the same thermometer which only a moment before had been used to 
ascertain the temperature of the atmosphere. The mercury in the scale immediately 
sunk to 32 0, 3 Fahr., or three tenths below that of the atmosphere, and it was main- 
tained at that standard for fifteen minutes, while the temperature of the atmosphere 
was still slowly rising. At the expiration of that time the pupa was slightly com- 
pressed with the forceps, and its temperature rose slowly to 32 0, 7, that of the atmo- 
sphere being 32 0, 8. In this observation there was not the objection of part of the 
bulb of the thermometer being exposed, nor of evaporation taking place from the 
surface of the wetted bulb. Hence it is fair to conclude that the internal tempera- 
ture of a pupa, perfectly at rest, is scarcely above that of the surrounding medium, 
when the temperature of that medium is stationary. We have still further evidence 
that this is really the case, when instead of a single specimen a considerable number 
of pupae are employed. When the bulb of a thermometer was completely covered 
with the pupae of the Flesh Fly, Musca vomitoria , Linn., the temperature of the atmo- 
sphere being 56 0, 5 Fahr., the mercury was not in the slightest affected, but continued 
exactly at the same standard. But when the more delicate pupae, or nymphs, are 
employed, as those of Bees, the temperature of a number of them which have been 
somewhat disturbed is generally a little above that of the surrounding medium ; and 
this is also the case when a single specimen is employed, if its temperature be taken 
during the summer, when the nymph is active and preparing to pass into the perfect 
state, as shown in Table III., No. 39. But this difference very soon becomes reduced 
2 n 2 
