AUGUST 213 



presently into a maggot, which spends probably the next 

 two years in burrowing and eating a gallery, ever widen- 

 ing as the larva grows, and emerges ultimately a full- 

 fledged insect. How long it lives as a maggot, and how 

 many weeks or months it spends in the chrysalis stage, 

 has not been ascertained, for it is obviously difficult to 

 follow the proceedings of a creature which inhabits solid 

 timber ; but some exceedingly interesting details may be 

 gathered of its invisible movements. Fabre has shown 

 that, while feeding, the grub always gnaws its way parallel 

 with the wood-fibres that is, in a direction parallel with 

 the longitudinal axis of the tree. But when it has com- 

 pleted its larval and pupal stages, and obeys the impulse 

 to get to the open air, it does not travel back along the 

 gallery which it has formed. That would have to be 

 scooped out afresh, for the bore of the tunnel has always 

 been increasing as the grub grew. Acting upon some 

 inscrutable intelligence, the perfect insect cuts a new 

 road at right angles to the old one, and therefore across 

 the grain of the wood, leading the shortest way to the 

 outside. We creatures of grosser sense, who so easily lose 

 our way in a London fog, may well wonder what is the 

 faculty by which this fly, fully equipped for flight and 

 freedom, yet which has never seen the light of day, can 

 steer its way to sunshine through the darkness and solid 

 timber in which it has spent all its life. 



One would think that the young Sirex was pretty 

 secure from molestation while pursuing its way through 

 the heart of a fir-tree, but nature is very impartial in pro- 

 viding every living creature with its special enemy, and 

 has not neglected the wood-wasp in that respect. Its 

 flight is marked by a large species of ichneumon fly 



