The Problem of the SIrex 



I find numbers of specimens of a black 

 Buprestis {B. octoguttata) in the old stumps 

 of pine-trees left standing in the ground, 

 hard outside but soft within, where the wood 

 is as pliable as tinder. In this yielding sub- 

 stance, which has a resinous aroma, the 

 larvae spend their life. For the metamor- 

 phosis they leave the unctuous regions of the 

 centre and penetrate the hard wood, where 

 they hollow out oval recesses, slightly flat- 

 tened, measuring from twenty-five to thirty 

 millimetres ^ in length. The major axis of 

 these cells is always vertical. They are 

 continued by a wide exit-path, sometimes 

 straight, sometimes slightly curved, accord- 

 ing as the tree is to be quitted through the 

 section above or through the side. The exit- 

 channel is nearly always bored completely; 

 the window by which the insect escapes opens 

 directly upon the outside world. At most, 

 in a few rare instances, the grub leaves the 

 Buprestis the trouble of piercing a leaf of 

 wood so thin as to be translucent. But, if 

 easy paths are necessary to the insect, pro- 

 tective ramparts are no less needed for the 

 safety of the nymphosis; and the larva plugs 

 the liberating channel with a fine paste of 

 masticated wood, very different from the or- 



1 .975 to 1. 17 inch. — Translator's Note. 

 215 



