MR. NEWPORT ON THE RESPIRATION OF INSECTS. 
553 
Treviranus has very justly observed*, that the quantity, or I should rather say 
the activity of respiration in insects, is increased with the increase of atmospheric 
temperature. At the same time the law which has been established by Dr. Edwards 
with regard to the respiration of vertebrated animals, is equally applicable to insects, 
namely, that supposing the activity of respiration to be exactly of the same degree at 
two extremes of atmospheric temperature, say 32° Fahr. and 60° Fahr., there would 
be a greater quantity of oxygen consumed at the lower than at the higher tempera- 
ture. It is necessary to bear all these circumstances in mind, and also the compa- 
rative size of the insect, in estimating the amount of its respiration. Thus the larvae 
of Lepidopterous insects appear to respire a greater quantity of atmospheric air in a 
given time than the perfect insects or pupae ; but it must be remembered that they are 
in general very much larger in bulk, sometimes even double that of the perfect insect, 
and consequently consume a greater quantity of air. But if we examine larvae which 
are of the same cubic bulk as their perfect insects, we shall find that, provided they 
continue in a state of activity, the respiration of the perfect insects will be much 
greater than that of their larvae, as is shown in the observations on Papilio urticce , 
Linn, in its different states, Table I., No. 1 1 to 20. It is there seen that the greatest 
amount of respiration is during the perfect state, and that the period when an insect 
which undergoes all its changes during a few weeks in the summer has the lowest de- 
gree of respiration, is about one or two days after it has entered its pupa state, as shown 
in the accompanyingTable, No. 15. This is the condition of respiration during summer, 
when all the changes in the insect are continuous. The observations referred to in 
the Table were made upon larvee which had not attained their full size, No. 12 to 14. 
But if a larva has arrived at its full size when the observation is made, it then ap- 
pears to respire much more in a given time than the perfect insect. But this is not 
really the case. The observation is illusive, and arises, first, from the larva being al- 
most always in a state of activity, and consequently having a more rapid consumption 
of oxygen^ and next because it is frequently at least two thirds larger than the perfect 
insect. Thus the full-grown larva of Oilonestis potatoria, Steph., is about '26 of a 
cubic inch in bulk, while the perfect insect is not more than TO. When the larva 
and perfect insect of this species were confined separately in glass stoppered phials of 
the same dimensions, IT 4, at the same temperature, 66° Fahr., the larva became 
asphyxiated in nine hours, while the perfect female was still living and vigorous at 
the expiration of twenty-four hours. In this case the larva was almost constantly in 
motion, while the perfect insect was quiet and resting. On a prima facie view of this 
observation it would appear that the larva respires a greater quantity of air, compared 
with its bulk, in a given time, than the perfect insect. It is a well established fact, 
that among the higher animals respiration is at its minimum during sleep. It is 
neither so frequent nor so voluminous, and consequently there is less oxygen con 
sumed. This has been long known with regard to the human species ; but, as shown 
* Lancet, vol. ii. 1835, p. 456. 
MDCCCXXXVI. 4 B 
