The Problem of the Sirex 



ceed my requirements; they are strikingly 

 regular; they afford the compasses the full 

 space needed for accurate measurement. 



Before calling In geometry, let us, If pos- 

 sible, name the creator of these beautiful 

 curves. The Inhabitants of the poplar have 

 disappeared, perhaps long ago, as Is proved 

 by the mycelium of the agaric; the Insect 

 would not gnaw and bore Its way through 

 timber all permeated with the felt-like growth 

 of the cryptogam. A few weaklings, how- 

 ever, have died without being able to escape. 

 I find their remains swathed In mycelium. 

 The agaric has preserved them from de- 

 struction by wrapping them In tight cere- 

 ments. Under these mummy-bandages, I 

 recognise a Saw-fly, Sirex augur, KLUG., 

 in the state of the perfect Insect. And — 

 this is an Important detail — all these adult 

 remains, without a single exception, occupy 

 spots which have no means of communica- 

 tion with the outside. I find them some- 

 times in a partly-constructed curved passage, 

 beyond which the wood remains intact, some- 

 times at the end of the straight central gal- 

 lery, choked with sawdust, which is not con- 

 tinued in front. These remains, with no 

 thoroughfare before them, tell us plainly that 

 the Sirex adopts for Its exit methods not 



223 



