CHAPTER VIII 



THE PROBLEM OF THE SIREX 



1 I ^HE cherry-tree supports a small jet- 

 ■*■ black Capricorn, Cerambyx cerdo, 

 whose larval habits it was as well to study 

 in order to learn whether the instincts are 

 modified when the form and the organization 

 remain identical. Has this pigmy of the 

 family the same talents as the giant, the 

 ravager of the oak-tree? Does it work on 

 the same principles? The resemblance be- 

 tween the two, both in the larval state and 

 in that of the perfect insect, is complete ; the 

 denizen of the cherry-tree is an exact replica, 

 on a smaller scale, of the denizen of the oak. 

 If instinct is the inevitable consequence of the 

 organism, we ought to find in the two in- 

 sects a strict similarity of habits; if instinct 

 is, on the other hand, a special aptitude fa- 

 voured by the organs, we must expect va- 

 riations in the industry exercised. For the 

 second time the alternative is forced upon 

 our attention: do the implements govern the 

 practice of the craft, or does the craft gov- 

 ern the employment of the implements? Is 

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