46 NATURAL SELECTION in 



this point Mr. A. Sidgwick, in a paper read before the Rugby 

 School Natural History Society, gives the following original 

 observation : " I myself have more than once mistaken Cilix 

 compressa, a little white and gray moth, for a piece of bird's 

 dung dropped upon a leaf, and vice versd the dung for the moth. 

 Bryophila Glandifera and Perla are the very image of the 

 mortar walls on which they rest ; and only this summer, in 

 Switzerland, I amused myself for some time in watching a 

 moth, probably Larentia tripunctaria, fluttering about quite 

 close to me, and then alighting on a wall of the stone of the 

 district which it so exactly matched as to be quite invisible a 

 couple of yards off." There are probably hosts of these re- 

 semblances which have not been observed, owing to the diffi- 

 culty of finding many of the species in their stations of natural 

 repose. Caterpillars are also similarly protected. Many 

 exactly resemble in tint the leaves they feed upon ; others are 

 like little brown twigs, and many are so strangely marked or 

 humped, that when motionless they can hardly be taken to be 

 living creatures at all. Mr. Andrew Murray has remarked 

 how closely the larva of the peacock moth (Saturnia pavonia- 

 minor) harmonises in its ground colour with that of the young 

 buds of heather on which it feeds, and that the pink spots 

 with which it is decorated correspond with the flowers and 

 flower-buds of the same plant. 



The whole order of Orthoptera, grasshoppers, locusts, 

 crickets, etc., are protected by their colours harmonising with 

 that of the vegetation or the soil on which they live, and in 

 no other group have we such striking examples of special 

 resemblance. Most of the tropical Mantidae and Locustidse 

 are of the exact tint of the leaves on which they habitually 

 repose, and many of them in addition have the veinings of 

 their wings modified so as exactly to imitate that of a leaf. 

 This is carried to the furthest possible extent in the wonder- 

 ful genus, Phy Ilium, the " walking leaf," in which not only 

 are the wings perfect imitations of leaves in every detail, but 

 the thorax and legs are flat, dilated, and leaf-like ; so that 

 when the living insect is resting among the foliage on which 

 it feeds, the closest observation is often unable to distinguish 

 between the animal and the vegetable. 



The whole family of the Phasmidae, or spectres, to which 



