CH. x.] NATURAL SELECTION. 25 



Turning now to the insect world, we find a vast abundance 

 of corroborative proof. Among the tiger-beetles examined 

 by Mr. Wallace in the Malay islands, those which lived upon 

 wet mossy stones in mountain brooks were coloured velvet 

 green ; others, found for the most part on dead leaves in the 

 forest, were brown ; others again, &quot; never seen except on the 

 wet mud of salt marshes, were of a glossy olive so exactly 

 the colour of the mud as only to be distinguished when the 

 sun shone,&quot; by casting a shadow. &quot; In the tropics there are 

 thousands of species of insects which rest during the 

 day clinging to the bark of dead or fallen trees; and the 

 greater portion of these are delicately mottled with grey and 

 brown tints, which though symmetrically disposed and 

 infinitely varied, yet blend so completely with the usual 

 colours of the bark, that at two or three feet distance they 

 are quite indistinguishable.&quot; Moths, which when resting 

 expose the upper surfaces of their wings, have these dull- 

 coloured. Butterflies, on the other hand, which rest with 

 their wings raised perpendicularly and laid together so as 

 to show only the under surfaces, have the upper surfaces 

 brilliantly coloured, while the exposed under surfaces are 

 dusky and inconspicuous, or even marked in imitation of 

 leaves. Mr. Wallace describes an East Indian butterfly 

 whose wings are superbly tinted with blue and orange : this 

 butterfly is a very swift flyer and is never known to settle 

 save among the dead leaves in the dry forests which it 

 frequents. When settled, with its wings raised, it imitates a 

 shrivelled leaf so perfectly that even the keen eye of the 

 naturalist can hardly detect it. This protective colouring is 

 found throughout the whole immense order to which belong 

 grasshoppers, crickets, and locusts ; the most remarkable 

 instance being furnished by the so-called &quot; walking-leaf,&quot; to 

 which no description can do justice. On the other hand, 

 hornets, bees, and wasps, which are protected by their stings, 

 we brilliantly but not in general protectively coloured. Bugs 



