262 
MR. NEWPORT ON THE TEMPERATURE OF INSECTS. 
with each other, will seldom if ever both indicate precisely the same amount of tem- 
perature in exactly the same space of time. The mode of taking 1 the temperature is 
either by allowing the insect to remain with the soft ventral surface of its abdomen 
pressing against the bulb of the thermometer when in a state of rest, or by pressing 
the thermometer firmly against its body when in a state of excitement, the insect 
being held during the time between a pair of forceps covered with woollen, in order 
that the contact of the fingers of the operator may not interfere with the correctness 
of the observation by unnaturally increasing the temperature of the insect. It is also 
further necessary to guard the hand with a glove, or non-conducting substance, to 
prevent the thermometer itself from becoming affected by it during the experiment. 
Much caution also is necessary when the same thermometer is employed to ascertain 
the temperature both of the atmosphere and of the excited insect, to guard against 
one very material source of error. It is necessary first to ascertain the temperature 
of the atmosphere, and then that of the insect, because if this be not attended to, and 
the experiment be made by taking the temperature of the insect before observing that 
of the atmosphere, the moisture on the bulb of the instrument occasioned by the con- 
densation of the cutaneous perspiration from the body of the animal will occasion 
during its drying or evaporation, while taking the temperature of the atmosphere, an 
indication of a lower amount of atmospheric temperature than what really exists, and 
consequently the apparent difference between the temperature! of the insect, pre- 
viously taken, and that of the atmosphere, will be much too great, and thereby appear 
to indicate a higher temperature than what the body of the insect really possesses. 
When the temperature is taken during a state of rest, the thermometer is placed 
beneath, and as completely covered by the abdomen of the insect as possible, while 
a second thermometer, which has been very carefully compared with the first, is 
placed on the same level with and at a short distance from it to indicate the tem- 
perature of the atmosphere. When the temperature of active volant insects is to be 
taken, it is preferable to inclose them singly in a small phial, introducing them with 
the forceps as before, and being particularly careful not to touch the phial with the 
fingers. The degree of activity or quiescence of the insect must always be parti- 
cularly noticed, and also the number of inspirations. By attending to these facts we 
acquire a knowledge of the amount of respiration compared with the quantity of 
heat evolved, as indicated by the thermometer. The temperature of the insect taken 
on the exterior of the body is always a little lower than that of the interior ; but the 
difference is not so great as might at first be imagined, so that I have generally pre- 
ferred taking the exterior temperature, because the observations are then less com- 
plicated by unnatural causes. The interior temperature is seldom if ever more than 
a degree and a half, or at most two degrees above the exterior, and often not even 
half a degree, when the insect is in a state of perfect rest. Perhaps it may be urged 
as an objection, that when the bulb of the thermometer is applied to the exterior of 
the body, it can seldom be so completely covered as to indicate the whole amount of 
