The Problem of the Sirex 



the worm of the cherry-tree leaves the sur- 

 face and penetrates into the wood to a depth 

 of about two inches, leaving behind it a wide 

 passage, which is hidden on the outside by a 

 remnant of bark that has been discreetly 

 spared. This spacious vestibule is the fu- 

 ture insect's path of release; this screen of 

 bark, easily destroyed, is the curtain that 

 masks the exit-door. In the heart of the 

 wood the larva finally scoops out the cham- 

 ber destined for the nymphosis. This is an 

 egg-shaped recess an inch and a quarter to 

 an inch and three-quarters in length by two- 

 fifths of an inch in diameter. The walls are 

 bare, that is to say, they are not lined with 

 the blanket of shredded fibres dear to the 

 Capricorn of the Oak. The entrance is 

 blocked first by a plug of fibrous sawdust, 

 then by a chalky lid, similar, except in point 

 of size, to that with which we are already 

 familiar. A thick layer of fine sawdust 

 packed into the concavity of the chalky lid, 

 completes the barricade. Need I add that 

 the grub lies down and goes to sleep, for the 

 nymphosis, with its head against the door? 

 Not one forgets to take this precaution. 



The two Capricorns have, in short, the 

 same system of closing their cells. Note 

 above all the lens-shaped stony lid. In each 

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