Il8 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



the yellow flecks on the elytra and thorax, is of a uniform brown 

 colour. 



The weevils differ from the bark beetles in one important 

 biological feature. They make no mother gallery, and their 

 eggs are laid either singly as in Hylobius, or in groups as in 

 Fissodes, from outside the bark, being deposited through a hole 

 gnawed for the purpose. 



In other respects the biology of the two families is somewhat 

 similar. The members of both are long lived and indulge in 

 recuperative feeding; that is, they renew their reproductive 

 capacity by a period of restful feeding between their flight 

 periods. This is one of the most interesting and important 

 features of their biology. The well-known and very injurious 

 damage done by the adult Hylobius in young plantations, the 

 boring in the young pine twigs so typical of Myelophilus, the 

 gnawing of the younger twigs and branches by the adult Fissodes, 

 all these are a preparation for reproduction. 



Accordingly the work or "damage" of our pine beetles is 

 divisible into two distinct types — the damage, or to use a most 

 useful, if vague, term, the frass, caused during the breeding 

 period, and during the feeding or recuperative period. Now it 

 is noteworthy that in many cases the " breeding " ground of a 

 species is not necessarily its "feeding" ground. Hylobius 

 " feeds " on young, newly-planted conifers, and even on birch 

 and oak, but it never breeds on these. Its "breeding" ground 

 is the Scots pine stump. So too with Myelophilus. It "feeds" 

 on the young pine twig, but it breeds in the stem. The same 

 is true of Hylastes ater, which is strangely similar to Hylobius 

 in its life-history. It " feeds " on young conifers and breeds on 

 the Scots pine roots. As I hope to show later this feature in 

 the biology of these beetles is of the first importance in dealing 

 with our pine beetle problems. 



From the point of view of the forest entomologist, the Scots 

 pine may be divided into three regions, namely, crown and 

 branches, stem, and stump and roots. Each of these regions 

 has its peculiar beetles. 



In the crown the following occur : — 

 {a) Breeding — T. acwninaius, 



P. bidentatus. 

 {b) Feeding — M. piniperda. 

 F. pini. 



