M. H. Rathke on the Respiratory Process in Insects. 97 
2. Or it may be too hairy or plumose to allow such a move- 
ment to be perceived by the eye ; 
3. Or it may have fasted for a long time, rendering the move- 
ments so few and weak as to escape observation ; 
4, Or the insect may be rendered dull and weakly by other 
causes. 
Here the author remarks that in insects in general respiration 
by no means plays so great a part, and, although necessary, is 
not so important as in birds and mammalia*. Many proofs of 
this assertion are to be found, according to the author, in Sorg’s 
memoir, ‘ Digestiones physiologice circa respirationem insecto- 
rum et vermium’ (Rudolst.: 1804) ; and he cites the circum- 
stance that many insects live in the earth or in rotten wood, 
where they cannot possibly obtain an abundance of pure air for 
their respiration. He also cites the observation of Sir Humphry 
Davy (‘Consolations in Travel,’ Dialogue 2), that on the small 
floating islands of Conferve in a lake near Tivoli he found an 
immense number of the most various insects, although this lake 
exhales so much carbonic acid and sulphurous vapour, that the 
aquatic birds, which sometimes visit it, remain on its shores, 
because, on the lake itself, these vapours would be fatal to them. 
Moreover his own observations show that in many insects the 
respiratory movements are few and weak. 
If the above-described movements of the abdomen have really 
an influence upon respiration, this must be a double one, in con- 
* In a note subsequently written, the author observes :—‘ This is 
going too far, as appears from the experiments of Treviranus on the 
respiration of the lower animals (Treviranus and Tiedemann’s ‘ Zeitschr. 
fiir Physiol.’ Bd. iv.). 
* Results.—1. The quantity of oxygen taken up and of carbonic acid 
exhaled by the same insect is very different in equal times, according as it 
moves or rests, according as it is exposed to a higher or lower temperature 
(greater in the former case), and according as it is full-fed or fasting. 
‘(In Apis terrestris the quantities of carbonic-acid gas exhaled at 9-12° 
R. and 14-23° R. are as 22: 174.) 
«2. The quantity of carbonic-acid gas produced in respiration differs in 
different insects. ‘The most active insects exhale the most carbonic acid, 
Among these are the Bees, Humble Bees, and Lepidoptera. These are 
followed by the Syrphi and probably many other Diptera. Then come 
the Libellule and Beetles. The smallest amount of carbonic acid is ex- 
haled by the larve of Lepidoptera and Beetles. A larva of Cetonia aurata 
does not exhale a fifth of that produced by the perfect insect of the same 
species. 
“3. When the temperature of the air is 113° R. the Bee produces nearly 
as much, and at a temperature of 22° R. far more carbonic acid than even 
the Dove. Papilio Atalanta, even when it has been for several days with- 
out food, exhales a far greater quantity of the gas at 15° R. than that bird. 
Cats, Guinea-pigs, and Rabbits are inferior to Humble Bees in strength of 
respiration at a temperature of 16-179 R. At this temperature Syrphus 
nemorum is about equal to those animals.” 
Ann. § Mag. N, Hist, Ser. 3, Vol. ix. 7 
