MR. NEWPORT ON THE TEMPERATURE OF INSECTS. 
311 
while strings of air bubbles issue from the spiracles, particularly from the posterior 
ones ; an interval of a few moments succeeds, and then another contraction follows, 
and more air-bubbles issue forth; and this alternate contraction of the segments, and 
expiration of bubbles, takes place until the insect is completely asphyxiated, while 
its body becomes contracted both in length and diameter. From these circum- 
stances it seems highly probable that the contraction of the longitudinal muscles of 
the body of the larva, during its progressive motions, are connected with the expi- 
ratory act of respiration of the insect, just as similar parts in the body and thorax of 
the perfect individual of the species are connected with the respiratory functions 
during the motions of flight. In every condition of the insect the number of respi- 
rations is in accordance with the activity of the animal, and with the quantity of air 
it deteriorates in a given time, and they are also in accordance with the amount of 
heat developed. Thus in the pupa state I have not observed more than three in- 
spirations per minute, and these only when the pupa has been disturbed ; and the 
number of these corresponds with the small amount of respiration, and the low power 
of generating heat in this condition. In the perfect insect of the same species, the 
Sphinx, when in a state of excitement after great exertion. Table V. No. 21, I have 
counted forty-two, but at the expiration of an hour and a quarter, No. 23, when the 
insect had become quiet, there has been only fifteen inspirations per minute. In the 
Hive Bee and Humble Bees, the number of respirations has amounted to from one 
hundred and ten to one hundred and twenty, when in a state of excitement, but when 
very moderately active, to no more than forty. The same, and even greater difference, 
is found in the Wild Bee, Anthophora retusa, Steph., in which, in a state of violent 
excitement, the number of respirations once amounted to two hundred and forty in a 
minute*; while in the very same insect when first removed from its hybernaculum 
in the autumn, or in the spring of the year, and when it has a temperature only a little 
above that of the medium in which it has been living, it has scarcely more than two 
or three respirations in the same space of time. In the common Green Grasshopper, 
when moderately excited. Table VI. Nos. 11, 12, and after it had fasted during se- 
veral hours, there were about thirty-seven or thirty-eight. In all these cases the 
number corresponds with the amount of respiration or quantity of air deteriorated. 
2. Velocity of the Circulation. 
But there is not merely an accordance between the activity of the insect, its quan- 
tity of respiration, and amount of heat developed, but also between these and the 
general rate of pulsation, or the circulation of the blood in its body. This therefore 
demands our particular attention. 
When an insect is remaining perfectly at rest, its rate of pulsation, like its respira- 
tion and temperature, is greatly diminished. We are enabled to observe the pulsa- 
tion of the heart, or dorsal vessel, both in the larva and perfect state of many insects, 
* Philosophical Transactions, 1S36, Part II. p. 550. 
