544 Appendix. 



can concern us. But in the pupae of nearly-allied species 

 of which the larva; feed on kindred plants in the same 

 districts at the same periods of the year, can the enemies 

 be so different as to produce such a considerable diver- 

 gence in form ? One might answer this question in the 

 negative with some confidence, and affirm that in this 

 case the difference in the pupae does not result from 

 the ' divergence in the mode of life,' or from the dif- 

 ference in the external conditions, but is accidental, 

 i. c. a consequence of some fortunate variation induced 

 by some external cause, which variation afforded pro- 

 tection against common foes to one species in one 

 way, and to the other species in some other way ; this 

 course, once entered upon, having been urged on by 

 natural selection, until at length the wide divergence 

 now shown is attained. How in the case of any of 

 the species the peculiarity in colour or form can actually 

 serve as a protection, I must confess myself at fault in 

 answering. Only in the case of the pupa of Eueides 

 Isabella will I venture to offer a supposition. That it 

 is not green like other pupae which suspend themselves 

 among foliage (Siderome, Epicalia, Callidryas, &c.), but 

 contrasts more or less brightly with the dark green of 

 the leaves, precludes the idea of concealment ; on the 

 other hand its colour is too dull to serve as a conspicuous 

 sign of distastefulness. In either case the meaning of 

 the wonderful processes of the pupa would remain un- 

 explained. 



" We are thus compelled to seek another possibility in 

 mimicry, by which foes would be deceived by deceptive 

 resemblance. But what is the object imitated ? Dead 

 insects overgrown by fungi are often found on leaves, 

 the whitish or yellowish fungi growing from their bodies 

 in various fantastic forms. Such insects of course no longer 

 serve as tempting morsels. The processes of the pupa of 

 Eneidcs suggest such fungoid growths, although I cer- 



