THE WOOD-WASP 



99 



21. THE WOOD-WASP {Sirex) 



The wood-wasp of fir-trees, though very common in northern 

 Continental countries, is only met with now and then in 

 England. A large wasp-like fly, an inch-and-a-half long, 

 which hums as it flies, and is armed with what looks like a 

 terrible sting, is perhaps discovered in some house or shop, 

 captured by the boldest man about, and sent to the local 

 naturalist for examination. Some disappointment follows 

 upon his report that 

 the insect is not a 

 hornet, that it has 

 no sting, and that, 

 though capable enough 

 of mischief, it never 

 wounds man or any 

 other animal. In its 

 early stages it dwells 

 in fir-trees. The egg 

 is laid in timber, 

 standing or felled. 

 The larval Sirex de- 

 vours the wood, run- 

 ning long, winding 

 galleries along the 

 trunk ; it pupates 

 within the tree, and 

 finally emerges in the 

 winged form, to per- 

 petuate the race. Sirex only shows itself in England casually, 

 but it often appears many at a time, and does much harm. It 

 is not unlikely that our attacks are due to recent importations 

 of live insects from the Continent. Wood containing larvse 

 may be stored and even cut up without hindering the de- 

 velopment of one or more wood-wasps, which may, perhaps, 

 give rise to a local infestation. 



The fly wears the colours of a wasp, black and gold, but 

 has not the narrow waist, nor yet the sting of a true wasp. 

 It has four membranous wings, and biting mouth-parts. Since 

 it undergoes complete transformation, and does not exhibit 



Fig. 60. — Female wood-wasp (S. gigas). 

 Natural size. 



