PROTECTIVE COLORATION. 105 



pillar, renders it inconspicuous. There is one group of cater- 

 pillars which, in addition to a prevailing green or brown colour, 

 lias a most striking resemblance in form to twigs or buds. 

 This resemblance has been long noticed. Messrs. Kirby and 

 Spence, in a chapter dealing with the " Means of Defence of 

 Insects," in their " Entomology," remarked upon these cater- 

 pillars as follows : " There is a certain tribe of caterpillars, 

 called surveyors (Geoun'trce), that will sometimes support 

 themselves for whole hours, by means of their posterior legs, 

 solely upon their anal extremity, forming an angle of various 

 degrees with the branch on which they are standing, and looking 

 like one of its twigs. Many concurring circumstances promote 

 this deception. The body is kept stiff and immovable, with the 

 separations of the segments scarcely visible ; it terminates in a 

 knob, the legs being applied close, so as to .resemble the bud at 

 the end of a twig; besides which it often exhibits intermediate 

 tubercles, which increase the resemblance. Its colour, too, is 

 usually obscure, and similar to that of the bark of a tree. 

 So that, doubtless, the sparrows and other birds are frequently 

 deceived by this manoeuvre, and thus baulked of their prey. 

 Rosel's gardener, mistaking one of these caterpillars for a dead 

 twig, started back in great alarm when, on attempting to break 

 it off, he found it was a living animal." 



The protective colour and form of some of these geometrid 

 larva? have been carefully studied and described by Mr. Poulton 

 in an admirable series of papers,* the results being summed 

 up in his book " The Colours of Animals." The caterpillars 

 are generally long and cylindrical in form, of the same or 

 nearly the same diameter throughout : the greater part of the 

 body lies between the anterior and posterior legs, and this 

 structural fact is largely responsible for the twig-like appear- 

 * In Trans. Entorn. Noc., 18858. 



