TRACHEATES I 93 



had protective colouring on the unseen parts as well 

 were no better off than their comrades. They were 

 therefore not specially selected, and they lost their 

 shades in their descendants by crossing. 



The animal is still safer when its colouring is 

 associated with certain peculiarities of shape so as to 

 imitate an object. 



The outer side of the wings of the tortoise-shell 

 butterfly has zigzag lines, so that it looks like a decaying 

 leaf when at rest. In the lappet-moth there is a most 

 deceptive resemblance to a heap of dried oak-leaves 

 owing to the colour and the crinkled edges and position 

 of the wings. One of our moths, the Xylina vetusta, 

 looks just like a broken piece of wood — an effect 

 which is increased by the creature "shamming death." 

 There are also many geometer-moth caterpillars that 

 closely resemble twigs, and even have warts on their 

 bodies that look like the unopened buds on the twig. 

 Further, the animals stretch themselves out stiffly when 

 at rest, and then rise up at a steep angle from the 

 branch on which they are, so that they look just like 

 an offshoot of it. 



But the adaptations of insects go a good deal further 

 than this. They not only imitate lifeless objects, but 

 even other animals that are not likely to be touched. 

 Bees and wasps are generally protected by a sting, and 

 most animals know these weapons and respect their 

 owners. We must not be surprised to learn, therefore, 

 that certain harmless insects have the dangerous aspect 

 of the stinging insects, and so enjoy the same 

 immunity, A species of fly, the Eristalis, strikingly 



