SUSPENSION OF PUP^. 277 



jfixed to the silk in such a manner as to sustain its 

 weight ; but careful examination discovers that it has 

 been furnished with an efficient apparatus for this 

 purpose, in a number of very minute hooks, similar 

 to those of the pro-legs which have been sloughed off. 

 Feeling about then with its tail for the silk, it insinu- 

 ates these hooks among the meshes, and being no 

 longer in danger of falling, it can swing secure, 

 as it had previously done in the caterpillar state. 



Reaumur has, however, seen some chrysalides 

 fall before they completed the process, in conse- 

 quence, as he thinks, of having spun too slight a 

 mesh-work of silk. In order to ascertain the cor- 

 rectness of this inference, we tried a series of experi- 

 ments upon a considerable number of a brood of the 

 peacock butterfly {Vanessa lo), the same upon which 

 Reaumur made his observations. We allowed some 

 to spin only half the usual portion, and removed them 

 to another station. Here they eagerly recommenced 

 the task, and, if left unmolested, never fell from the 

 spot; but if previously removed a second time, they 

 seldom succeeded in completing the process in the 

 usual way. They did not, indeed, in such cases, 

 attempt spinning an imperfect silken suspensory ; but 

 abandoning in despair what they felt themselves in- 

 capable of performing, they crept dov/n to the bottom 

 of the nurse box, and cast their skins without having 

 anything to which they could attach themselves.* 



When the hooks of a chrysalis have been properly 

 fixed among the meshes, it remains suspended con- 

 tiguous to the skin which it has just cast ; but not 

 liking the neighbourhood of its now useless spoil, it 

 sets itself to get rid of it. For this purpose it con- 

 torts itself in various ways, sometimes assuming a 

 figure similar to an S, so that it may push against 



* J. R. ^ 



VOL. VI. 24 



