556 
MR. NEWPORT ON THE RESPIRATION OF INSECTS. 
the ground 42 0, 8 Fahr. For nearly a month before this, the pupae had been subject 
to the common influences of the season: there had been severe frost, the thermome- 
ter having sometimes sunk down to 20° Fahr. At the expiration of twenty-four 
hours the phials with the pupae were removed from the ground, and their gaseous 
contents very carefully tested with pure lime-water, and gave the usual most unequi- 
vocal signs of respiration having taken place, but only in a slight degree. The tem- 
perature of the air a few inches above the ground was only 31° Fahr., that of the soil 
four inches beneath the surface 35 0, 2 Fahr. ; so that it was clear the pupae had con- 
tinued to respire to within two or three degrees of the freezing-point, and perhaps 
even at very nearly that temperature. That the pupae were still living and active, was 
proved by one of them once or twice contorting its abdomen when removed from 
the earth, before the stoppers of the bottles were withdrawn. The pupae were then 
buried again as before, the temperature of the atmosphere and of the soil continuing 
respectively at 35° - 2 and 31° Fahr. I then exposed another pupa in a stoppered phial 
on the surface of the ground for twenty-four hours. At eight o’clock on the follow- 
ing morning the thermometer stood at 16°’5 Fahr. ; so that the pupa was then sup- 
porting a temperature of 15 0, 5 Fahr. below freezing. At the expiration of the twenty- 
four hours the temperature of the atmosphere had again risen to 31 0, 2 Fahr. and the 
phials were again examined. The temperature of the soil four inches below the sur- 
face was 33 0- 5 Fahr. In No. 3, which had been exposed on the surface of the ground, 
there was only the very faintest trace of carbonic acid gas, but sufficient to satisfy me 
that the pupa had respired. The phials Nos. 1 and 2 were then examined. In both 
there were incontestible proofs of the presence of carbonic acid gas ; thus clearly in- 
dicating that the pupae had respired freely at a temperature of 33 0- 5 Fahr., and in a 
slight degree even below 32° Fahr. 
Although the pupae employed on the above occasions had borne so low a tempera- 
ture, they were not injured, since the whole of them have produced perfect insects*. 
That a pupa which has been constantly exposed, for forty-eight hours, to a tempera- 
ture of five degrees below freezing does not become frozen, I am fully satisfied, having 
once made a very careful examination in order to ascertain this point. The pupa was 
taken from its exposed situation with a pair of forceps, in order that it might not be 
touched with the fingers, and have its temperature increased, and a horizontal incision 
was instantly made with a sharp scalpel through the posterior part of its body, which 
separated the dorsal from the ventral surface. All the parts immediately collapsed 
when exposed to the open air, and the muscles were almost as tense as during a state 
of activity ; the fat was of its usual whiteness, and the dorsal vessel was exactly as it 
appears during any other period, excepting that it was a little contracted in diameter, 
but its contents were fluid. When the body of the pupa was cut through, the fluid 
flowed as usual ; but I could not observe any motion of the dorsal vessel, nor any 
* June 1836. 
