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XXIV. On the Respiration of Insects. By George Newport, Esq. Member of the 
Royal College of Surgeons, and of the Entomological Society of London. Com- 
municated by P. M. Roget, M.D. Sec. R.S. 
Received and Read June 16, 1836. 
Respiratio?i. 
It has been long proved by many physiologists that insects produce the same changes 
in the atmosphere during respiration as other animals. Reaumur, Bonnet, Scheele, 
Huber, Edwards, Audouin, and others, have all shown that the results of the respi- 
ration of atmospheric air by insects are the production of carbonic acid gas, and the 
loss of oxygen ; but these results vary in degree in different genera, — in the different 
states of the same insects, — and at different periods of the year. My object, therefore, 
in this paper will be to show the relative quantity of air consumed by different tribes 
of insects in their different states, — the power which particular insects have of sup- 
porting existence in different media, — and the relation which this power and the con- 
sumption of air bear to the comparative volume of the structures concerned. 
The life of an insect has been considered by naturalists to have three distinct pe- 
riods, the larva, the pupa, and the perfect state ; but each of these periods, in so far as 
the functions of the different structures of the body are concerned, although tending 
only to the production of the perfect individual, is in itself a distinct condition. Thus 
the respiration, circulation, temperature, food, and locality of the insect are in general 
all different in the different states. In the earliest period of the larva state the respi- 
ration is much feebler than when the animal has nearly arrived at its full size, and 
the circulation of its blood is much quicker ; but the relative quantity of its food is 
much greater, in proportion to its bulk, in the latter than at the earlier period, and 
its power of generating heat increases as it approaches to its adult condition. In the 
pupa state also there is a change in all these functions. In many genera the insect 
ceases to eat ; its circulation becomes slower than at any other period ; its respiration 
is greatly diminished in frequency and volume ; and its power of generating and of 
maintaining a temperature of body above that of the surrounding medium, which 
every individual insect constantly preserves when in a state of activity, is now almost 
suspended. In the perfect, or imago, state there are other changes in these functions. 
The respiration again increases in frequency and volume ; the power of generating 
and of maintaining heat is very much augmented ; the circulation is more rapid than 
at any other period, while the necessity for a constant supply of food is often less 
3 Y 
MDCCCXXXVI. 
