vi INSTINCT 83 



It thereupon 



" sewed up the rent ; and not only so, but ' the scissors having 

 cut off one of the projections intended to enter into the con- 

 struction of the triangular end of the case, it entirely changed the 

 original plan, and made that end the head which had been first 

 designed for the tail.' " l 



Lastly, according to Dahl, 2 a spider will not only repair 

 an injury to its web if sufficiently serious, but if it finds 

 that a thread which it has spun does not fit the rest of 

 the network, it will reject that thread and substitute 

 another. 



The converse case to the repair of damage is the 

 utilisation of a special opportunity so as to dispense with 

 unnecessary labour. Thus we find, again, according to 

 Kirby and Spence, that the 



u common cabbage caterpillar, which, when building web 

 under stone or wooden surfaces, previously covers a space with a 

 web to form a base for supporting its dependent pupa ; when 

 building a web beneath a muslin surface dispenses with this 

 base altogether. It perceives that the woven texture of the 

 muslin forms facilities for attaching the threads of the cocoon 

 securely enough to support the weight of the cocoon without 

 the necessity of making the usual square inch or so of basal 

 ipport." 3 



'his instance 4 is thrown into relief by the conduct of 

 Huber's caterpillar, which has been already referred to. 



. . . " P. Huber has described a caterpillar which makes, by 

 a succession of processes, a very complicated hammock for its 



1 An entomological friend remarks on this story that the caterpillar 

 vould probably (as in the previous example) merely set about to spin a 

 )iece of web where it was exposed, and this would have the effect, not 

 )lanned by the insect, of "sewing" the edges together. If so, both this 

 md the previous example show how an adaptive modification would 

 result from the persistence with which the instinct operates until it is 

 satisfied. 



2 Dahl, p. 166 ff. 3 Romanes, p. 237. 



4 A parallel is the action of the dung beetle, which normally makes 

 pellets for its eggs, but utilises any that it finds ready made. (Quoted 

 from Kirby and Spence by Romanes, M.E.A. p. 244). Mr. Romanes 

 goes much too far in calling this an " intelligent adaptation." On the face 

 of it, it is merely an instance where an appropriate object calls out the 

 instinctive reactions, that part of the normal instinctive operation which is 

 rendered unnecessary remaining suppressed. 



G 2 



