The Problem of the Sirex 



ages full of irregular curves; it bends it in 

 an arc which allows it to turn about; and, 

 with its head held plumb with the adjacent 

 surface, it goes straight ahead by the nearest 

 way. 



The most extraordinary obstacles are 

 powerless to turn it aside from its plane 

 and its curve, so imperative is its guiding 

 force. It will gnaw metal, if need be, rather 

 than turn its back upon the light, which it 

 feels to be close at hand. The entomo- 

 logical records place this incredible fact be- 

 yond a doubt. At the time of the Crimean 

 War, the Institut de France received some 

 packets of cartridges in which the bullets had 

 been perforated by Sirex juvencus; a little 

 later, at the Grenoble Arsenal, S. glgas carved 

 himself a similar exit. The larva was in 

 the wood of the cartridge-boxes; and the 

 adult insect, faithful to its direction of escape, 

 had bored through the lead because the near- 

 est daylight was behind that obstacle. 



There is an exit-compass, that is incon- 

 testable, both for the larvae preparing the 

 passage of deliverance and for the adult in- 

 sect, the Sirex obliged to make that passage 

 for himself. What is it? Here the prob- 

 lem becomes surrounded with a darkness 

 which is perhaps impenetrable; we are not 

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