vii DEFENCES OF INSECTS 271 



two first abdominal segments it possesses a large eye- 

 like spot, not in any way specially attractive when the 

 insect is undisturbed, though the marks are somewhat 

 grotesque (see Fig. 52). But upon the approach of an 

 enemy, the caterpillar instantly telescopes its head and 

 thoracic rings into the segments that bear the spots. 

 These segments thus become swollen, and look like the 

 head of the animal, upon which four seeming eyes are 

 very noticeable and terrible of aspect. The incon- 

 spicuous insect is at once changed into a serpent-like 

 form, sufficiently surprising to frighten away any would- 

 be assailant (see Fig. 53). Mr. Poulton states that it is 

 the cobra that is simulated in these cases. Like other 

 snakes it has not a large head, and its eyes are small. 

 It inspires fear by its dilated hood with its great eye- 

 like 'spectacles,' and these features the caterpillar 

 copies in its swollen anterior end and terrifying spots. 

 It is extremely interesting, Mr. Poulton remarks, that 

 the caterpillar should imitate a feature which is merely 

 deceptive in the snake itself. 



The assumption at will of a like mimetic resemblance 

 is to be found in the larva of the Puss Moth (Cerura 

 vimda, see Fig. 54). When at rest this caterpillar 

 harmonises with the colour of its surroundings, and is 

 well concealed. But as soon as it is disturbed it with- 

 draws its head into the first body-segment, dilating the 

 margin, which is of a red colour, and on which there are 

 two black spots, like two eyes. An appearance is pro- 

 duced of a huge flat vertebrate face (see Fig. 55). The 

 caterpillar also turns and confronts the enemy. Human 

 beings are alarmed by the attitude, and doubtless it is 

 a protection against the most audacious vertebrate foes 



