132 PROTECTION OF WOODLANDS. 



(a.) INSECTS ON CONIFEROUS TREES. 



I. BEETLES OR CHAFERS (Coleoptera). 



A. BARK-BEETLES (Scolytidaz). 



64. Bark-beetles (Scolytidse) in General. 



The bark-beetles include some of the most destructive insect 

 enemies of our coniferous woodlands, and although a few species 

 are also to be found on broad-leaved species of trees, yet as they 

 mostly live in the sap wood, they are less injurious as well as 

 less numerous. Their number is very large, but in the following 

 only the most important species can be treated of. As the habits 

 and the life-history of the various genera and species have much that 

 is common to all of them, a short general description thereof may 

 be given before proceeding to consider the species in detail. 



The bark-beetles are small, often very small, insects, almost 

 cylindrical in shape, and of quiet, indefinite colour, which spend 

 all their life, with the exception of the short time of swarming and 

 reproduction, in the inside of woody fibrous plants, within which 

 they develop from the ovum. For the most part they hibernate 

 as perfect insects ; but some of them are very early afoot in 

 spring, and swarm during the first warm days of March, or even 

 in February, whilst others only make their appearance again in 

 April or May, so that they may be divided in this respect int 

 early swarmers and late swarmers. 



For the purpose of ovi-deposition they select, in the fi] 

 instance, the class of timber most suitable, preferring neithe 

 wood that is dead or that has already grown too dry, nor sounc 

 healthy trees, whose strong flow of resin would destroy the beetle 

 and larvae of most of the species ; stems in any way damaged, am 

 sickly, windfall trees, or those injured and broken by wind or 

 accumulations of snow and ice, newly felled timber, the stum] 

 left in the ground from recent clearances, and crops of backw* 

 growth constitute the most favourable breeding-places. The 

 beetles bore as quickly as possible into the sapwood of the stei 

 selected, choosing for convenience the fissures on thick-barke 

 Pine trees. In the case of species which only enter in 

 within the stem, there is generally a comparatively large hollo 

 cavity under the bark, the copulating chamber or cat 



