LEAF-BUTTERFLY. 177 



and actually imitate the form of leaves growing on their 

 native branches. These butterflies (scientifically known 

 as Oaliima ) have the npjier surface of the wings lirilliantly 

 marked with orange, their front wings terminating in a 

 sharp point externally, and the hind ones in a "tail," 

 after the fashion of our swallow-tailed butterflies. Between 

 the sharp point of the front and the tail of the hind wing 

 there runs on the under surface a curved line, from which 

 smaller lines are given off to the edges of the wings. 

 When this butterfly settles on the stem of a ])lant bearing 

 pointed leaves, and closes its wiags, the points and tails of 

 the same of course come into exact opposition ; and since 

 the tail of the wings is closely applied to the stem of the 

 plant it appears exactly as though it were the stalk of a 

 leaf, the midrib and veins of which are exactly imitated 

 by the lines on the imder surface of the wings ; while the 

 apex of the leaf is formed by the opposed points of the 

 front wings. So exact is the resemblance of the butterfly 

 when in this po-ition to a faded leaf, that, as Mr. Wallace 

 tells us, it deceives the eye even when gazing full upon it, 

 and without actually seeing the insect settle upon the spot 

 it is absolutely impossible to find it. To increase the 

 delusion uo two individuals of these insects are precisely 

 alike on the under surface ; while many of them have little 

 black patches, or clots, exactly resembling the dark fungous 

 growths so often found on decaying leaves. Fortunately 

 for the reader who desires to verify this extraordinary 

 instance of inanimate mimicry, a case is now exhibited in 

 the central hall of the Natural History Museum with 

 several of these insects attached to a bough with faded 

 leaves, and it is curious to watch the visitors to this case 

 and see how often they fail to distinguish all the butter- 

 flies from the leaves which they imitat-e. 



The next best instance of inanimat-e mimicry among 

 insects occurs in the so-called stick- and leaf -insects, which 

 are allied to our gras.shoppers and cockroaches. The 

 stick-insects, some of which are found in southern 

 Europe, have long, slender bodies and limbs, of a dark 

 colour, and so exactly resemble dry sticks that it is almost 

 impossible to distingui.sh between the one and the other. 



