COLOURS OF ANIMALS. 37 



=as a tiger's stripes, according to Mr. Wallace, imitate 

 very closely the foliage and trees amidst which, it 

 ^crouches. The camel's coat is sandy like its desert ; 

 4ind the rabbits offer as plain examples as any of the 

 colour-harmony in question. The polar bear is white, 

 like the arctic fox in winter dress ; and the nocturnal 

 rats and moles are dressed in shades the opposite of 

 the ghost-like hues that become so conspicuous at night. 

 But, descending to still lower grades of life, we may 

 discover examples of this "mimicry/' not only of 

 surroundings, but also of lifeless or inorganic objects, 

 and of, it may be, plant structures as well, on the part 

 of animals. The so-called "stick insects/' or "walking 

 twigs," as they are often called the Phasmidcc of the 

 naturalist present us with the most perfect reproduc- 

 tions of bits of dried twigs. A figure of one of these 

 insects is before me as I write. It is represented 

 climbing on the delicate branch of a shrub, and but 

 for the expectation of what one is looking for, there 

 would be considerable difficulty in determining which 

 is insect and which plant. The bodies of these "twig 

 insects " which belong, by the way, to the Orthoptera, 

 or that order which harbours the familiar crickets and 

 grasshoppers are represented by mere lines. The 

 wings have disappeared, and it has been remarked, 

 that in their gait these insects exhibit a peculiar habit 

 of using their legs in a singularly awkward fashion, 

 and thus apparently aid the illusion of the spectator 

 .that he is regarding a dried twig, moved erratically 

 by the wind. 



