270 ROMANCE OF THE INSECT WORLD CHAP. 



only moves in this way when it is hunting, at other 

 times it goes in a straight line ; but its little imitator 

 zig-zags always." And while it is customary for 

 spiders to remain nearly motionless when they are 

 eating, picata " acts like an ant which is engaged in 

 pulling some treasure-trove into pieces convenient for 

 carrying. I have noticed a female picata which, after 

 getting possession of a gnat, kept beating it with her 

 front legs as she ate, pulling it about in different 

 directions, and all the time twitching her ant-like 

 abdomen." The ants mimicked are abundant, and as 

 a rule are exempt from persecution. The spiders on 

 the contrary are particularly relished by insectivorous 

 birds, so that there seems good reason for inferring 

 that this mimicry is protective. 



Lastly we arrive at the most extraordinary cases of 

 Mimicry, in which the defenceless species assumes the 

 outward dress of a protected form belonging to a 

 different sub-kingdom. Mr. Bates was startled by the 

 strong resemblance of a large South American cater- 

 pillar to a small snake. The first three segments 

 behind the head were dilatable at pleasure, and on 

 either side it had a great black pupillated mark, 

 imitating an eye. That a poisonous snake was 

 suggested was evident by the appearance of keeled 

 scales on the crown, produced by the recumbent feet, 

 as the caterpillar raised the anterior end of its body. 

 Among our British caterpillars, that of the Large 

 Elephant Hawk Moth (Chcerocampa elpenor] affords 

 a similar example. It occurs in two varieties, a green 

 and a brown, both being in protective keeping with 

 the colour of their food-plant. On each side of the 



