86 MIND IN EVOLUTION CHAP. 



the tender young leaf fails it) it shaves off one membrane 

 of an old leaf, and uses that. 1 More remarkable, if 

 correctly reported, is the account given by Romanes of a 

 spider which, being so injured that it could not spin 

 effectually, took to stalking its prey. 2 Not only will a 

 hungry wolf attack a man from whom he would otherwise 

 fly, but according to Dahl, 3 a fasting spider, which was 

 normally shy of dangerous insects, fought fiercely with a 

 wasp. The contrast between the ordinary gentleness of 

 the female of many mammalia and her fierceness and 

 bravery in defence of her young is in reality another case 

 in point. An example both of persistence in overcoming 

 obstacles and of variation in method is supplied by the 

 larva of Cecidipta excoecaria. 



u The female moth lays an egg on a gall, and the resulting 

 larva bores into the gall and nourishes itself on the interior till 

 all is eaten except a thin external coat ; the caterpillar then 

 pupates in this chamber. The galls vary in size and shape, and 

 the larva displays much constructive ability in adapting its home 

 to its needs by the addition of tubes of sillc or by other modes. 

 Sometimes the amount of food furnished by the interior of the 

 gall is not sufficient ; the larva, in such cases, resorts to the leaves 

 of the plant for a supplement, but does not eat them in the usual 

 manner of a caterpillar ; it cuts off and carries a leaf to the en- 

 trance of its abode, fastens the leaf there with silk, and then itself 

 entering, feeds, from the interior, on the food it has thus 

 acquired." * 



Lastly, the behaviour of crabs in finding means of 

 concealment gives examples both of the " mechanical " 

 and of the more adaptive type. Many crabs have the 

 habit of covering themselves with seaweed or other readily 

 adherent objects, the utility of the action lying in the 

 disguise. In one case, that of Dorippe, the habit appears 

 to have degenerated into a merely mechanical reflex, the 

 crab, as described by Schneider, constantly taking up bits 

 of stone, sponge, or anything else of suitable size and 

 shape, and fixing them on to itself. As it tears away one 



1 Schneider, p. 271. He notes it as a rare instance of an insect 

 altering a custom on encountering an obstacle, and thinks it implies a 

 certain degree of reflection. 



2 M.E.A. p. 209. 3 Op. cit. p. 178. 

 4 Cambridge Natural History ', VI. p. 424. 



