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MR. NEWPORT ON THE TEMPERATURE OF INSECTS. 
V. Temperature of Insects as connected with the other Functions of Life. 
On reviewing ail the circumstances connected with the temperature of insects, we 
cannot fail to observe the remarkable coincidence between the amount of heat pro- 
duced, and the quantity of respiration in these animals, under all the circumstances 
of their existence. We have seen that whether sleeping or waking, — whether inac- 
tive or in a state of great excitement, — the quantity of heat evolved by an insect is 
always in proportion to the quantity and activity of its respiration. But there are 
other circumstances which also claim our attention. When the temperature is in- 
creased, the circulation of the fluids of the insect are also much accelerated, and there 
is a greater amount of gaseous expenditure from the surface of the body. On the 
other hand it is observed, that when the process of digestion is suspended, not only 
is there a less expenditure of gaseous and fsecal matter from the surface of the body 
and from the alimentary canal, but the power and velocity of the circulation, the 
quantity of heat, and the activity of the respiration of the insect are diminished. 
These circumstances are readily demonstrated by experiments on insects, and lead 
us to inquire what relation subsists betw'een the great functions of life, and the 
production, and variations, of temperature in these “ little miniatures of creation,” 
and whether the temperature of their bodies depends mainly upon one or more of 
these functions, or upon the agency of that inexplicable source of ail the voluntary 
energies of the animal, — the nervous system. 
1. Respiration. 
The circumstances which affect the respiration of insects have been particularly 
considered on a former occasion *. It was then seen that the contractions of the seg- 
ments of the body in insects correspond with the acts of respiration in other animals, 
and that these are greatest during a state of activity, and less frequent during a state 
of repose. It is exceedingly difficult to determine the number of these respiratory 
motions, per minute, in the larva state, even of the large Lepidopterous insects, and 
to ascertain what relation they bear to the temperature, quantity of respiration, and 
rate of pulsation of the dorsal vessel ; but from a great number of observations on 
the larva of the Sphinx in its fifth or last period, I am inclined to think that they are 
not so frequent as in the perfect insect. It has been suggested by some naturalists that 
since the progressive movements of the larva are mainly performed by means of the 
longitudinal contractions of the body, that these are concerned in the function of re- 
spiration, and this appears highly probable from the circumstances which take place 
when a larva is submerged in spirits of wine or other fluid for the purpose of destroy- 
ing it. At first it does not appear to be incommoded by contact with the spirit, but as 
soon as it attempts to inspire it is immediately affected, and the four posterior segments 
contract, and the whole body becomes shortened, as in the act of forcible expiration, 
* Philosophical Transactions, 1836, Part II. p. 547. et seq. 
