208 DARWINISM chap. 



which has just that amount of irregular curvature that is seen 

 in dry and withered leaves. The colour is very remarkable 

 for its extreme amount of variability, from deep reddish-brown 

 to olive or pale yellow, hardly two specimens being exactly 

 alike, but all coming within the range of colour of leaves in 

 various stages of decay. Still more curious is the fact that 

 the paler wings, which imitate leaves most decayed, are 

 usually covered with small black dots, often gathered into 

 circular groups, and so exactly resembling the minute fungi 

 on decaying leaves that it is hard at first to believe that the 

 insects themselves are not attacked by some such fungus. 

 The concealment produced by this wonderful imitation is 

 most complete, and in Sumatra I have often seen one enter a 

 bush and then disappear like magic. Once I was so fortunate 

 as to see the exact spot on which the insect settled ; but even 

 then I lost sight of it for some time, and only after a per- 

 sistent search discovered that it was close before my eyes. 1 

 Here we have a kind of imitation, which is very common in a 

 less developed form, carried to extreme perfection, with the 

 result that the species is very abundant over a considerable 

 area of country. 



Protective Resemblance among Marine Animals. 



Among marine animals this form of protection is very 

 common. Professor Moseley tells Us that all the inhabitants 

 of the Gulf-weed are most remarkably coloured, for purposes 

 of protection and concealment, exactly like the weed itself. 

 " The shrimps and crabs which swarm in the weed are of 

 exactly the same shade of yellow as the weed, and have white 

 markings upon their bodies to represent the patches of Mem- 

 branipora. The small fish, Antennarius, is in the same way 

 weed-colour with white spots. Even a Planarian worm, which 

 lives in the weed, is similarly yellow-coloured, and also a 

 mollusc, Scyllsea pelagica." The same writer tells us that" " a 

 number of little crabs found clinging to the floats of the blue- 

 shelled mollusc, Ianthina, were all coloured of a corresponding 

 blue for concealment." 2 



1 Wallace's Malay Archipelago, vol. i. p. 204 (fifth edition, p. 130), with 

 figure. 



2 Moseley's Notes by a Naturalist on the Challenger. 



