226 



PROTECTION AGAINST INSECTS. 



b. Life-history. 



The chief swarming period of this beetle, which lives from 

 1 to 2 years, is in the spring or early 

 summer (May or June) ; hut pairing 

 and reproduction go on throughout the 

 whole of the warmer season up to Sep- 

 tember, so that no real period for 

 swarming exists. Copulation generally 

 takes place on the ground. 



The eggs are laid from May to Sep- 

 tember on stumps and roots of the 

 Scots pine and spruce, preferably on 

 ljl/l : those of trees felled about 18 months 



: -f 1 before. The under-surface of roots 

 and especially of those which project out 



I HI \ of the ground is preferred. Hiber- 



nating beetles continue egg-laying in 

 the spring. 



The larvae appear after 2 to 3 weeks, 

 and up to the middle of October eat gal- 

 leries sometimes a metre long (Fig. 91) 

 in the bast and sap wood of the stumps 

 and roots ; the burrows continually 

 increase in breadth, and are filled with 

 wood-dust. The larvae, at least those 

 which have been hatched in the autumn, 

 pass the winter at the end of these 

 galleries. They do no injury of any 

 economic importance, their sources of 

 food being confined to valueless wood. 



In the following spring, after having been 

 dormant for about 9 months, the larvae 

 pupate in the stump or roots, in a cocoon 

 constructed of wood-fibres and boring- 

 dust. The pupal state lasts about 2 to 8 

 weeks. The perfect insects emerge from 

 May till September of the second year. 

 The period of disclosure thus extends 

 over four months, corresponding to the 



Fig. 91. Scots piue root 

 bored by H. abietis, L. 



a Boring free from wood- 

 dust. 



b Boring full of wood-dust. 



c Longitudinal section of 

 pupal chamber. 



d Transverse section of 

 pupal chamber. 



e Flight hole. 



/ Entrance to pupal cham- 

 ber closed with bitten 

 wood. 



