Sept. 1, 1867.] 



HARDWICKE'S SCIENCE-GOSSIP. 



193 



THE DISGUISES OE INSECTS. 



By ALFRED R. WALLACE, E.R.G.S, F.L.S., M.E.S. 



i VERY one has beard 

 of the wonderful 

 Leaf-insect of the 

 tropics, which is 

 scarcely less a puz- 

 zle to the scientific 

 naturalist than it 

 is to the natives of the coun- 

 tries it inhabits. I have been 

 told over and over again by 

 intelligent persons in the East 

 of the curious plaut whose 

 leaves changed into insects ! 

 And I could never convince 

 them that this was not the 

 true explanation, for they 

 would say, "It is no good 

 your trying to persuade me, for 

 I have seen the creature myself; 

 and I assure you that it has real leaves growing 

 out of it, exactly the same as the other leaves that 

 grow upon the tree." And we really cannot wonder 

 at this belief, for when the creature is alive it re- 

 mains motionless among the foliage, and the 

 colour, veining, form, and texture of its wing-covers 

 and appendages, are so wonderfully like those of 

 leaves that it is extremely difficult to distinguish it 

 at all. 



A few years since a specimen of the Phyllium 

 scythe, the " Walking Leaf " of India, was kept 

 alive at the Royal Botanic Garden at Edinburgh. 

 Mr. Andrew Murray wrote a long account of it, and 

 among other matters says : " It so exactly resembled 

 the leaf on which it fed, that when visitors were 

 shown it, they usually, after looking carefully over 

 the plant for a minute, declared that they could sec 

 no insect. It had then to be more minutely pointed 

 out to them; and although seeing is notoriously 

 said to be believing, it looked so absolutely the 

 same as the leaves among which it rested, that this 

 No. 33. 



test would rarely satisfy them ; and nothing would 

 convince them that there was a real live insect 

 there but the test of touch — it had to be stirred up 

 to make it move, or taken off the plant to crawl on 

 the finger of the attendant." 



But these remarkable insects do not stand alone. 

 There are many others in every order which are 

 " disguised " in a somewhat similar manner, some 

 with equal perfection, others less accurately, but 

 all serving the same purpose— that of protecting 

 the insect from the enemies that would destroy it. 

 I propose now to give a short account of some of 

 the more interesting cases that occur both at home 

 and in the more luxuriant regions of the tropics. 



Almost every one must have noticed the very 

 different way in which the bright colours are dis- 

 tributed in butterflies and moths. In the former, 

 the whole upper surface of the wings is adorned 

 with equally gay colours, while the under surface is 

 always less brilliant, and is generally blotched or 

 mottled with obscure or simple hues. In most 

 moths, on the contrary, the bright colour is re- 

 stricted to the upper surface of the lower wings, 

 the upper wings being usually of variously mottled 

 brown or ashy tints. This difference is at once seen 

 to be connected with the habits of the insects, the 

 conspicuous colours being so arranged as to be 

 visible during flight, but hidden in repose. On the 

 other hand, the beautiful mottlings and spots and 

 delicate shadings that cause so many moths to re- 

 semble bark or lichens, or leaves or twigs, are never 

 developed on those parts of the wings which are 

 hidden during repose. Thus all the Bombycidse and 

 Noctuidaj, which conceal their hind wings when at 

 rest, have them either quite plain or ornamented 

 with rich orange or crimson hues ; while almost all 

 the Geometridai, which rest with their wings spread 

 open, and such of the Bombycida? as have the same 

 habit, are mottled and tinted alike on both front 

 and hind wings. 



K 



