MR. NEWPORT ON THE TEMPERATURE OF INSECTS. 
263 
heat developed. But this objection, although at first plausible, must be considered 
valid only when the observations are made very quickly. But even were the objec- 
tion substantiated it would be of but little consequence, because it is only the relative 
amount of heat developed by one insect as compared with that of another, when the 
observations on both are conducted in a similar manner, which is ultimately sought 
for, it being almost impossible to ascertain the exact amount evolved by any single 
insect. It may also be urged as an objection to this mode of taking the temperature 
of insects in a state of excitement, that when an insect is respiring very rapidly, the 
friction of the segments of its body against the bulb of the thermometer may evolve 
a certain amount of heat independent of the natural heat of the insect, and thereby 
indicate a higher temperature in the insect than that which really exists. In 
order to meet this objection, I made a number of trials with my thermometers, by 
using, as nearly as could be ascertained, about the same amount of attrition against 
the bulb of the instruments as that which is exerted by the segments of the excited 
insect during its laboured respiration and efforts to escape, and found that so small a 
quantity of heat is evolved that it is not in the slightest degree indicated on the scale 
of the thermometer. Hence I have not in general found it necessary to take the tem- 
perature of the interior of the body, although I have done so in a few instances, be- 
cause there are also other circumstances which interfere with the correctness of the 
observation. The first of these is the large size of the instrument employed compared 
with that of the body of the insect into which it is inserted, and the consequent ne- 
cessary loss of a certain amount of caloric, which becomes latent in the thermometer, 
before there is any indication of increased temperature on the scale, and because also 
of the unavoidable escape of a large amount of caloric into the surrounding atmo- 
sphere, and because still further it is only at the very instant after the introduction of 
the thermometer into the body of the insect that the real perceptible amount of tem- 
perature is indicated, while the insect under observation is every moment losing the 
power of generating and of maintaining its temperature, owing to the injury that has 
been inflicted upon it. These objections do not occur when the observations are made 
on the exterior of the insect, which from its being uninjured, continues to possess its 
power of generating heat unaffected by those circumstances which tend very mate- 
rially to interfere with or destroy it, while a sufficient length of time is afforded for 
the production of its full amount of heat after a certain quantity has become latent 
in the thermometer, before the observation of the amount is taken. 
These are the principal circumstances to be attended to in ascertaining the tem- 
perature of insects, and which have directed me in my observations. 
