320 
MR. NEWPORT ON THE TEMPERATURE OF INSECTS. 
bathed with perspiration. In the summer of 1832, I endeavoured to ascertain the 
quantity of gaseous expenditure in the larvae of Lepidoptera compared with the 
weight, quantity of food eaten, increase, and faecal expenditure of the insect, in a 
given time, and it was then found that the quantity of gaseous is equal to, or even 
greater than the quantity of faecal expenditure, even in these animals in which the 
latter is so enormous. The first subject of my observations was my old favourite, 
the larva of Sphinx ligustri. The specimen on which my observations were com- 
menced had been confined fasting about twelve hours, when it weighed 79’ 8 grains, 
having at the commencement of the twelve hours weighed 83*3 grains. During this 
period of fasting it had passed two masses of faeces, which weighed only 1’7 grain, 
consequently it had expended by the skin and respiratory organs 1’8 grain, an 
excess of one tenth of a grain in the gaseous expenditure. It was then supplied with 
fresh food, of which it ate 2’8 grains, and weighed 82’ l grains at the expiration of the 
first hour ; had passed no faeces, but had expended ’5 of a grain from the skin and 
respiratory organs. It was then made to fast for an hour, and afterwards weighed 
again to ascertain whether there was any difference in the quantity of gaseous ex- 
penditure during abstinence. It had discharged one mass of faeces weighing ’9 
of a grain, and itself weighed 80’8 grains, so that during the hour of fasting only 
•4 had passed off in the gaseous form instead of "5 as in the previous hour of 
taking food. At this time, while the insect was lying at rest, the dorsal vessel pul- 
sated at the rate of thirty-six beats per minute. The insect was then allowed to 
feed for another hour and weighed again; at the expiration of that time it had passed 
no feces, had eaten 3’4 grains of food, and weighed 83’6 grains. Thus one whole 
grain had now been expended in the gaseous form. It then fasted for three hours, 
but during that time it passed only one mass of fseces, which weighed 1*2 grains, and 
itself weighed 81’6, so that it had now lost only ’8 in the gaseous form during three 
hours’ fasting. It was thus evident that the greatest amount of gaseous expenditure 
occurs during the period of taking food, and that the quantity of gaseous expenditure 
decreases in proportion to the length of time the insect is kept fasting, and also that 
less gaseous expenditure takes place when there is the greatest amount of fecal, 
When the insect had been fed for another hour, and had eaten 2*7 grains of food, it 
weighed 83’9, but had passed no feces, consequently it had now expended ’4 of a 
grain in the gaseous form. It was thus evident that the quantity which passes off 
in the gaseous form during a certain length of time when the animal is taking food 
varies considerably, and sometimes amounts to one whole grain per hour, while at 
other times it is only about ’4 of a grain. These observations were continued 
through two successive days, wilh similar results. Thus after the insect had been 
fasting for twelve hours, during which time its amount of gaseous expenditure had 
been very trifling, the very first time it was weighed after feeding for one hour it had 
expended ’5 of a grain ; but when it was kept fasting, the very next hour its expendi- 
ture was only 4 of a grain. Similar experiments were also made at the same time 
upon the larvae of the Puss Moth, Cerura vinula, Steph., and Sphinx Elpenor, Linn., 
with precisely the same results relative to the quantity of gaseous expenditure. In 
