42 DECEPTIVE DEVICES 



pulse, the young caterpillars of some of the Nym- 

 phalidae, such as the Mourning Cloak (Euvanessa 

 antiopa), the American Tortoise-shell (Aglais mil- 

 berti), and Harris's butterfly (Cinclidia harrisii), 

 will move their heads by simultaneous jerks to one 

 side and the other, like a regiment of soldiers 

 shifting arms. This community of action must be 

 a very considerable safeguard, and indeed I am 

 inclined to regard the mere presence of caterpillars 

 in considerable numbers feeding in company as in 

 itself protective, partly because it is most common 

 in the highest family and never found in the low- 

 est, so that the habit would seem to have grown 

 and become intensified by its protective qualities. 

 Some certainly of the caterpillars which thus feed 

 in company will not be touched by chickens. I 

 have several times thrown twigs covered with the 

 caterpillars of the Mourning Cloak (Euvanessa an- 

 tiopa) into a chicken yard only to the alarm of the 

 chickens, they either paying no attention to the cat- 

 erpillars as they crawled away, or regarding them 

 with evident horror, never once offering to touch 

 them ; of course this may be due simply to their 

 spinous clothing. But besides the spined cater- 

 pillars which are presumably protected by such 

 community of action, such as the Mourning Cloak 



