The Problem of the Sirex 



corns. I am not selecting; I am recording 

 it in the order of my discoveries. The 

 Shagreen Saperda (S. carcharias) lives in 

 the black poplar; the Scalary Saperda (5. 

 scalaris) lives in the cherry-tree. In both 

 we find the same organization and the same 

 implements, as is fitting in two closely-re- 

 lated species. The Saperda of the Poplar 

 adopts the method of the Capricorn of the 

 Oak in its general features. It inhabits the 

 interior of the trunk. On the approach of 

 the transformation, it makes an exit-gallery, 

 the door of which is open or else masked by 

 a remnant of bark. Then, retracing its 

 steps, it blocks the passage with a barricade 

 of coarse packed shavings; and, at a depth 

 of about eight inches, not far from the heart 

 of the tree, it hollows out a cavity for the 

 nymphosis without any particular upholster- 

 ing. The defensive system is limited to the 

 long column of shavings. To deliver itself, 

 the insect will only have to push the heap of 

 woody rubbish back, in so many lots; the 

 path will open in front of it ready-made. If 

 some screen of bark hide the gallery from 

 the outside, its mandibles will easily dispose 

 of that: it is soft and not very thick. 



The Scalary Saperda imitates the habits of 

 its messmate, the Capricorn of the Cherry- 



