MR. NEWPORT ON THE TEMPERATURE OF INSECTS. 
271 
only left the pupa state about an hour and a quarter had a temperature of only *4 of 
a degree above the atmosphere; but at the expiration of two hours and a quarter, 
when it had become strong and had just taken its first flight, it had a temperature of 
5°*2 (Table V. No. 7-) ; while another specimen, which had been longer exerting 
itself in rapid flight, had a temperature of 9° above that of the atmosphere (Table V. 
No. 12.). Now these very species in their larva state, as we have before seen, have 
not more than 1°*3 and l 0- 8 above that of the atmosphere. The circumstances con- 
nected with the power of generating heat are nearly the same in the development of 
hymenopterous as in lepidopterous insects, the only difference being that those hy- 
menopterous insects which live in society have their heat augmented artificially before 
leaving the cocoon or pupa case. But when the young bee comes forth it parts 
with its temperature most rapidly, unless it be immediately protected by warmth af- 
forded to it by the bodies of other individuals. But when the same insect a few 
hours afterwards has become fully able to perform all the duties of its existence, it 
sometimes has a temperature of perhaps 20° Fahr. above that of the surrounding 
medium, while the temperature of its larva is scarcely more than 3° or 4° Fahr. 
During the whole of my observations I have not met with a single instance in 
which I was unable to detect a certain amount of external temperature in perfect 
insects in a state of activity, and it may therefore be regarded as proved that the 
whole class develop a certain amount of external heat. This uniformity of results, 
however, has not been observed in the experiments by Dr. Berthold *, before alluded 
to, and I can only attribute the discrepancy which exists between his observations 
and my own, to the circumstance of his omitting to attend particularly to the degree 
of activity or rest in the insects on which he experimented. I am the more inclined 
to attribute it to this omission, because in his 58th experiment, page 36, he says that 
in “ twenty chamber flies there was no development of heat or external temperature,” 
the observation being made in a steady atmospheric temperature of 17 Reaumur 
(70 o, 25 Fahr.). In my own observations upon insects of this order, as in an experi- 
ment with about the same number of specimens of Musca vomitoria, Linn, in their 
perfect state, the atmosphere being about 52° Fahr., the insects in a state of activity 
evolved from 1° to 1°’9 Fahr. of external heat, while in the same individuals in a state 
of partial rest the amount of heat did not exceed '6 of a degree. Again, in Dr. Ber- 
thold’s 59th experiment, which evidently was made in order to ascertain whether 
single insects evolve any appreciable heat, the bulb of a thermometer was passed 
into the body of a “ single chaffer,” through an opening under the wing-covers, and 
examined half-hourly for about two or three hours, but no heat was detected. In 
several experiments made by myself in a similar manner to this by Dr. Berthold, 
particularly on the Melolontha vulgaris, Steph. (Table VI. Nos. 45 to 52), the amount 
of heat developed varied from 2° to 9° above that of the atmosphere, and was always 
in proportion to the activity of the insect. 
* Neue Versuche, &c., p. 36. 
