104 M.H.Rathke on the Respiratory Process in Insects, 
inwards the segments of the abdomen may be rendered flatter, 
and by the others it may be shortened. By means of these 
latter muscles, moreover, the larva is enabled to curve its body 
sideways, upwards, and downwards. It is also of great importance 
to the larva, both in shortening and bending its body, that the 
epidermis and cutis of each segment form several small folds 
directed towards the body-cavity. 
In examining a living strong larva, it will be seen that it not 
unfrequently flattens its body greatly in places, and at the same 
time narrows it from the sides, and that this contraction of the 
body usually advances from before backwards over the different 
segments, no more than a few segments being contracted at the 
same time. The larva can likewise considerably shorten its body, 
when the increase of thickness does not appear to compensate 
fully for the abbreviation. But more commonly, and indeed 
when the larva endeavours to crawl, only partial shortenings of 
the body take place. 
§ 27. The exspirations must take place, theoretically, as in 
the Wasps and other Hymenoptera, when the body shortens, the 
individual segments not gaining so much in width as they lose 
in length, and also when the body curves to one side, but still 
more when it is flattened from above and below. ‘These views 
are confirmed by Bounet’s experiments on the respiration of 
Caterpillars. According to these experiments, when Caterpillars 
are immersed in water, more numerous and larger air-bubbles 
escape from the stigmata the greater the movements made by 
the animals. The inspiration must of course take place when 
the pressure upon the air-vessels, produced as above, ceases. 
As, moreover, the movements perceptible in the body-wall of 
Caterpillars and the larve of Beetles and Diptera are chiefly con- 
nected with the locomotion of these animals, it follows that their 
respiration is also chiefly connected with their locomotion. 
All respiration in these animals is subjected to the will, and 
never involuntary. 
§ 28. The Caterpillars of the Lepidoptera can shorten and 
elongate their bodies considerably, but can neither flatten them 
nor contract them at the sides in the same way as the larvee of 
the Scarabei. When they shorten themselves, the individual 
segments increase in width, but by no means sufficiently to com- 
pensate for the shortening. This applies also to the narrowing 
of the segments when the Caterpillar elongates itself. Some 
segments are usually elongated at the same time that others are 
shortened ; and the two processes take place progressively from 
before backwards. ‘This at lcast is the case during the locomo- 
tion of Caterpillars. 
