200 THE COLOURATION OF INSECTS 



the bark which they resemble. On Damba Isle one of 

 my natives came to tell me he had found some caterpillars 

 on a tree trunk, and when I went to look he showed me 

 three Lasiocampids, lying flat on the bark at a point 

 where its surface was somewhat irregular. While looking 

 at them and marvelling at the minute detail of the resem- 

 blance, I gradually became aware that the immediate 

 surroundings of these caterpillars were not bark but more 

 caterpillars, and much to the native's amazement, nine 

 of them were found lying closely packed side by side, and 

 utterly indistinguishable from the bark except by the 

 very closest inspection. These caterpillars fed at night 

 only,^ crawling up the trunk when the sun set and 

 returning to the same resting place next day. The 

 perfection of the concealment owes something to attitude. 

 The claspers are spread out sideways, so that the body 

 lies flat against the bark. The surface of the skin is 

 roughened by numerous little excrescences, and the gap 

 between the edge of the body and the bark is partly 

 obliterated by fleshy lappets, and often by short, 

 soft hairs. 2 



It is worth pointing out that a very large insect may 

 be concealed in a way that c nnot be believed, unless 

 it is actually seen in its natural surroundings. It is well 

 known that the caterpillar of the Privet Hawk Moth, 

 with its lilac and white oblique stripes, is not so conspicuous 



^ A colony of Eupterotidae caterpillars (Chrysopsyche varia) was found 

 on Bugalla Islo resting by day on a tree trunk. Wishing to obtain the 

 perfect moth I took some of the caterpillars and kept them in a large 

 circular glass topped box in which they rested quietly during the day. 

 .When evening came they formed the usual procession and atten>pted 

 to climb upwards, which of course they could not do. The result was 

 extremely absurd, for the caterpillars formed an endless chain, nose to 

 tail one behind another, which ceaselessly promenaded around the cir- 

 cumference of the box in the endeavour to find a path upwards. Although 

 there was plenty of food in the box they would not eat, since the proper 

 preliminary of marching t/jo the tree trunk had not been performed, and 

 I had to put the caterpillars back on the tree and hope to secure the 

 cocoons later. The limitations of instinct are here well shown. 



* See diagram in The Colours of Animals, p. 30. 



