90 ANIMAL COLOEATIOK. 



summarised hj Dr. Sharjj. '^ There is at present no evidence 

 at all that the light perceptions are sufficiently complex to be 

 entitled to be called seeing ; but that, as the large develop- 

 ment of the compound eye permits the simultaneous perception 

 of movement, its direction, and of lights and shades over a 

 certain area, a dragon-fly may pursue and capture another 

 insect without seeing it at all, in our sense of the word seeing." 



Nor is it quite certain that the colour vision even of birds is 

 precisely the same as ours : their sight in general seems to be 

 much keener, and possibly therefore they can see through an 

 insect disguise far more readily than we can, particularly when 

 keenness of vision is aided by hunger. It is said that when 

 a photograph of a green tree-frog or snake is examined the 

 animal is quite easily seen. The deceptive colour being 

 removed, the difference in form is at once apparent. 



It is clearly, therefore, premature to assert that colour 

 protection is in any way a means of defence against insect 

 enemies. It has been observed that animals which simulate 

 their surroundings constantly remain without movement ; this 

 is specially well seen in the case of various twig-like Geo- 

 meter larvtB, which, claspmg a branch firmly by the posterior 

 legs, stand out rigidly at an angle with the branch ; this 

 attitude, which of course increases their resemblance to a twig, 

 is maintained for hours. Indeed, absence of movement is 

 absolutely essential for protectively coloured animals, whether 

 they make use of their coloration for defensive purposes as 

 in the case of the caterpillars, or for offensive purposes like the 

 Mantis or spider. 



The power and the will to remain motionless is in itself 

 a most advantageous possession for an animal subject to the 

 attacks of carnivorous foes. Many insects will " feign death " 

 when pursued ; toads and frogs, as well as many reptiles, will 



