MR. NEWPORT ON THE RESPIRATION OF INSECTS. 
557 
dilatation of the tracheae ; so that the circulatory and respiratory motions must have 
been very nearly, if not entirely, suspended. After the pupa had been held between 
my fingers for a few seconds, there was a slight contraction of the longitudinal 
muscles, resembling a respiratory effort, and I observed a motion commencing like the 
peristaltic motion among the viscera. I thought I could also observe a slight motion 
in the dorsal vessel. All this distinctly proved that the pupa had not been frozen. It 
is thus certain that a very great degree of cold can be borne by these insects without 
injury, and that during the time it is borne the respiration of the insect is very nearly 
suspended. But it is not merely a great degree of cold that can be borne by 
these insects without injury, but a great and sudden change of temperature, from a 
comparatively warm to a very cold atmosphere, as was shown in the observation on 
No. 3, above noticed ; and even during that state the pupa will respire until the tem- 
perature has sunk below 32° Fahr. It is probable, that when the pupae are remain- 
ing entirely undisturbed in their natural haunts, they respire much less, and that if 
the suspension of respiration really does take place, when it has once occurred it con- 
tinues much longer than when they are removed from the soil and disturbed for the 
purpose of experimental observation, just as the sleep of the dormouse or bat will 
continue until the near approach of summer, although the animal is easily roused, 
and its respiration excited by external causes, even in the midst of winter. Yet it 
must be remarked, that when this takes place, whether the animal be one of the 
Mammalia or an insect which has arrived at its perfect state, it soon relapses again 
into its previous condition. 
In order to ascertain the comparative amount of respiration in the same species of 
insect at the same period of the year in different degrees of temperature, I confined 
two pupse of Sphinx ligustri in glass-stoppered bottles, inverted in a vessel of lime- 
water, and placed them on the ground in the open air, protected from the influence 
of the sun, and allowed them to remain for one hundred and fifty-six hours. During 
this time the temperature of the atmosphere was never lower than 35° Fahr., nor 
higher than 58° Fahr., being a range of 23 0, 6 Fahr. The temperature of the air at 
the time of inclosing the pupse was at 46° Fahr., and it was exactly the same when 
the contents of the bottles were examined. The amount of carbonic acid gas pro- 
duced by each of these pupse was 0T9 of a cubic inch. This was between the 12th 
and 20th of March. At the time of inclosing these pupse, I inclosed also another, 
which had previously been kept under precisely similar circumstances. This speci- 
men was placed in my room, where the temperature during night was never lower 
than 45°, and during the day not higher than 60°, being a range of fifteen degrees. 
At the time of inclosing this pupa the temperature of the room was 58°, and it was at 
the same standard when the bottle was examined, which was at the expiration of a 
hundred and eighty hours. The quantity of carbonic acid gas amounted to 0 - 40 of 
a cubic inch, being nearly double the amount produced by either of the pupse which 
were exposed to the open air; thus clearly proving that the relative quantity of respi- 
