THE COLOURS OF ANIMALS AND PLANTS 127 



they sit motionless for hours ; this absence of move- 

 ment being very important in order to increase the 

 deception. The head is modified in shape to in- 

 crease the resemblance to twigs, and a silk thread is 

 spun, attached to the twig, to relieve the tension 

 involved by remaining in the same position for so 

 long a time. They feed at night, when there is less 

 need for protective devices. The protection here is 

 so real that a green lizard will generally fail to detect 

 a stick caterpillar in its position of rest, though it 

 will seize and greedily devour it directly it moves. 



2. Adult Insects. — In butterflies the under surface 

 of the wings is coloured protectively, the upper surface 

 attractively ; and the sudden change when they fold 

 their wings over their backs is often enough to defy 

 detection. The most perfect examples are found in 

 the leaf butterflies, such as Kallima, found in the 

 Malay Archipelago, India, and Africa. This is a 

 very common and showy butterfly, with orange and 

 purple colouring on the upper surface of the wings. 

 It is a rapid flier, and frequents dry forests, always 

 settling where there is dead and decaying foliage. 

 The colouring on the under surface of the wings 

 bears a remarkable resemblance to that of a dead 

 leaf, and when the wings are turned up, with the head 

 and body hidden between them, it is often very 

 difficult to distinguish it from dead leaves, the 

 resemblance being rendered even more close by the 

 short tail, which looks like the stalk of a leaf, and by 

 the markings on the under surface, which closely 

 imitate the mid-rib and veins of a leaf. Speaking of 

 this insect, Mr. Wallace says : " The colour is very 



