338 OUTLINES OF EVOLUTIONARY BIOLOGY 



in this condition it is extremely difficult to detect them. Professor 

 Poulton remarks : 



"These caterpillars are extremely common, and between two and 

 three hundred species are found in this country ; but the great 

 majority are rarely seen because of their perfect resemblance to 

 the twigs of the plants upon which they feed." 



As will be seen from the illustration (Fig. 169), which represents 

 the larva of the brimstone moth upon its food plant, the hawthorn, 



the caterpillar is enabled to main- 

 tain its position for a long period 

 by attaching its head to a twig by 

 means of a silken thread. 



Numerous moths so closely re- 

 semble in the colour and pattern 

 of the upper surface of their wings 

 the objects upon which they rest 

 in the daytime, such as the bark 

 of trees, that they are almost 

 invisible, but perhaps the most 

 perfect examples of protective 

 resemblance are met with in the 

 wonderful leaf insects. Fig. 170 

 represents an orthopterous insect, 

 Pulchriphyllium crurifoliiim, from 

 Ceylon. The whole insect is of a 

 bright leaf-green colour, and not 

 only are the wings shaped and 

 veined so as to resemble leaves, 

 but even the body and legs exhibit 

 leaf-like outgrowths. 



In the well known Indian leaf 

 butterfly, Kallima (Fig. 171), the resemblance to a leaf is only 

 seen when the insect comes to rest with its wings folded together 

 above the body so as to expose their under surfaces. It is a dry, 

 dead leaf which is imitated this time, and stalk and midrib, veins 

 and colour markings, even down to such minutiae as rust spots, 

 are perfectly represented. 



The Mantidae or praying insects feed upon flies, &c., which 

 they capture with marvellous dexterity with their serrated claws. 

 In some species the uniform green colouration doubtless serves, 

 not only to protect them from their own enemies, but also to 



FIG. 170. A Green Leaf Insect 

 ( P ulchriphylUum crurifoliiim, 

 ?), from Ceylon; x . (From 

 a photograph.) 



