II.] INCIPIENT STRUCTURES. 45 



in Sumatra, and to capture many of them, and can vouch 

 for the accuracy of the following details. These butterflies 

 frequent dry forests, and fly very swiftly. They were seen 

 to settle on a flower or a green leaf, but were many times 

 lost sight of in a bush or tree of dead leaves. On such oc- 

 casions they were generally searched for in vain, for while 

 gazing intently at the very spot where one had disappeared, 

 it would often suddenly dart out, and again vanish twenty 

 or fifty yards farther on. On one or two occasions the in- 

 sect was detected reposing, and it could then be seen how 

 completely it assimilates itself to the surrounding leaves. 

 It sits on a nearly upright twig, the wings fitting closely 

 back to back, concealing the antennas and head, which are 

 drawn up between their bases. The little tails of the hind- 

 wing touch the branch, and form a perfect stalk to the leaf, 

 which is supported in its place by the claws of the middle 

 pair of feet, which are slender and inconspicuous. The 

 irregular outline of the wings gives exactly the perspective 

 effect of a shrivelled leaf. We thus have size, color, form, 

 markings, and habits, all combining together to produce a 

 disguise which may be said to be absolutely perfect ; and 

 the protection which it affords is sufficiently indicated by 

 the abundance of the individuals that possess it." 



Beetles also imitate bees and wasps, as do some Lepi- 

 doptera ; and objects the most bizarre and unexpected are 

 simulated, such as dung and drops of dew. Some insects, 

 called bamboo and walking-stick insects, have a most re- 

 markable resemblance to pieces of bamboo, to twigs and 

 branches. Of these latter insects Mr. Wallace says : 13 

 " Some of these are a foot long and as thick as one's finger, 

 and their whole coloring, form, rugosity, and the arrange- 

 ment of the head, legs, and antennas, are such as to render 

 them absolutely identical in appearance with dry sticks. 

 They hang loosely about shrubs in the forest, and have the 



13 Loc. cit., p. 64. 



