46 NATURAL SELECTION III 
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 versé 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 Mantide and Locustide 
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, Phyllium, 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 leaflike ; 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 Phasmide, or spectres, to which 
