MR. NEWPORT ON THE RESPIRATION OF INSECTS. 
555 
this very insect, soon after it was captured, the number of its respirations, in a mode- 
rate state of excitement, amounted to from one hundred and ten to one hundred and 
twenty per minute. I have recently observed the same difference between the number 
of respirations in a state of activity and quiescence in a female specimen of Sphinx 
ligustri in the perfect state. After the insect had been considerably excited in flight, 
it respired at the rate of forty-two per minute ; but when it had remained at rest 
about seventy-five minutes, its respiration had subsided to only fifteen per minute. 
This state of quiescence or profound sleep is the condition into which most insects 
fall at the close of summer, and in which they remain in their hybernacula during 
winter, when, if they be not disturbed, respiration becomes almost entirely suspended. 
This is the state of true hybernation. Lyonet has stated his belief that the respira- 
tion of pupse is entirely suspended for a very great length of time during winter ; but 
his experiments with the pupse of Sphinx ligustri, which led him to this statement, 
and which were made by merely covering the spiracles with soap-w r ater, and watch- 
ing with a microscope for the rising of bubbles, do not seem sufficiently precise and 
accurate to warrant the conclusion. For the purpose of ascertaining this fact, I 
made a number of observations in the year ] 829 upon the pupa of the Sphinx, and 
have since repeated them under different circumstances. There are different degrees 
of respiration at the same season of the year in pupse of different insects, which appear 
to have reference to the conditions in which the insects are placed in their natural 
haunts. When the Sphinx ligustri, which passes its winter in the earth, is examined 
in October or November, it gives most decisive proofs of respiration in the produc- 
tion of carbonic acid gas ; but this is much smaller in quantity than that which is 
produced at the same period in a given time, and under similar circumstances, by 
the pupa of Pavonia minor, Steph., which passes its winter in the open air, and is 
more readily exposed to the varied influences of the seasons. In both these insects 
the quantity of respiration is diminished as the winter advances. In December and 
January, respiration has subsided to its lowest state, and can be detected only with 
great difficulty while the insect remains undisturbed, but it does not entirely cease ; 
for if at that period the pupa be brought into a warm atmosphere of 45° Fahr. or 
upwards, it soon begins to respire more freely, and if placed in water or alcohol, a 
string of bubbles will be expired from the spiracles at each contraction of the seg- 
ments ; thus proving that a more powerful respiration is immediately induced when 
the insect begins to be aroused from its hybernating slumbers. It is only when the 
medium in which the insect is living is below 32° Fahr. that respiration is very nearly 
suspended. On the 1st of January 1836 I repeated my observations, which had 
originally been instituted in the winter of 1829. I removed four pupse of Sphinx 
ligustri from the ground, in which they had remained undisturbed for several weeks, 
and placed them in glass -stoppered bottles, three in one bottle and one in another, 
and buried them in the earth about four inches below the surface. The temperature 
of the soil at that depth was 37°‘5 Fahr., and of ihe atmosphere a few inches above 
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