SUSPENSION OF PUP^. 273 



which it is often engaged the greater part of a day, 

 and sometimes two, according to its strength. When 

 the first rent is made, however, the included chrysahs 

 soon wedges itseh' through the breach, the lower por- 

 tion swelling out greatly more than the upper, so as 

 to form an inverted but somewhat irregular cone. 

 The included insect continuing its laborious exertions 

 by successively contracting and dilating the rings of its 

 body, pushes off the now rent skin by degrees from the 

 head towards the tail, as the sack-racers mentioned 

 by Kirby would disengage themselves from the sacks 

 in which they were inclosed, or as one would roll 

 down a stocking from the leg. There are two cir- 

 cumstances worthy of notice in this process: the 

 position of the insect in hanging with its head down- 

 wards, throws a greater portion of the fluids of the 

 body towards the head, by means of their weight, 

 which swell out the part that splits; and also pushes 

 back the old skin, while the sloughing skin is pre- 

 vented from resiliating by a series of pegs, which act 

 like the toothed rack of a sluice-gate. The old skin, 

 being by these means pushed tov/ards the tail, is of 

 course compressed into several folds, which in some 

 degree prevent the extension of the rent, and serve 

 to keep the chrysalis from falling; for being now 

 detached from the skin, it has no hold upon the 

 meshes of the silk button, and is, in fact, at some 

 distance from it. 



This, then, is the part of the process where the 

 nicety of the mechanism is most worthy of admira- 

 tion; for the hooks by which the insect is in the lirst 

 instance suspended from the meshes of the silk are 

 sloughed otT, together with the skin, the grasp of 

 whose folds becomes then the only support of the 

 chrysalis. But this chrysalis, now deprived of feet, 

 and some distance from the suspensory cordage of silk, 

 has still to reach this, fix itself ther4| and cast off the 



