22 AKIMAL COLORATION. 



that they may be fairly set down to a coincidence having no 

 particular meaning. 



While it is easily intelligible that different structure, 

 different surroundings, and different food may produce differ- 

 ences of colour between larvfe and imagos, it is not so easy 

 to understand the colour changes which take place during the 

 caterpillar stage, or during the lifetime of an animal which 

 is born in a condition practically identical with that of its 



parents. 



In some cases it may be plausibly urged that the progressive 

 modifications in colour have a protective value ; but in other 

 cases this kind of argument cannot be used. 



The leaf insect {PhylUwm) has, in the adult condition, a most 

 extraordinary resemblance to a leaf ; the colour is green, and 

 the wing-cases are marked with lines which simulate the 

 veins of the leaf ; some of the joints of the limbs are flattened 

 and expanded. Mr. Andrew Murray relates* how an Indian 

 species exhibited in the Botanical Gardens at Edinburgh 

 deceived every person by its resemblance to the plant upon 

 which it lived. The deception was ultimately the cause of its 

 death ; for the visitors, sceptical as to its animal nature, insisted 

 upon touching it before they would be convinced. 



This insect when it is hatched from the egg has, as have the 

 Orthoptera (crickets, grasshoppers, cockroaches, etc.) generally, 

 a form but little different from that which it finally gets ; but 

 its colour is yellowish red, and not green. Directly it begins 

 to feed, its colour speedily changes to a light green ; this 

 coloiir gets mixed with yellow later in the year, suggesting 

 autumnal foliage, or at least a decaying leaf. 



The first change, from brown to green, looks very much as 

 if the food were alone responsible, and as if it were caused by 



* " Notice of the Leaf -Insect," Edhih. I\'ew Phil. Journal, Jan. 1856. 



