224 



PROTECTION AGAINST INSECTS. 



autumn, and passes the winter in these galleries or under 

 moss ; but occasionally its emergence is deferred till the 

 spring. Generation annual, sometimes lasting 2 years. 



c. Relations to the Forest. 



The black and white alder are preferred by it, then willows ; 

 but poplars and birch are also attacked. If attacking alder it 



selects young stems (2 to 4 

 years old), but older trees in 

 the case of willows. It is 

 therefore more dangerous to 

 the alder, and especially the 

 black alder. Willow-cuttings 

 are also attacked without 

 respect to species, and care- 

 less coppicing giving rise to 

 gnarled stools increases the 

 danger of infestation. 



The insect is injurious both 

 as a larva and imago. 



The beetle eats the bark 

 of young annual shoots down 

 to the sap-wood. The larva 

 then gnaws under the bark, 

 and bores obliquely upwards 

 or downwards into the wood 

 and often to the pith, thus 

 ruining the young stems, 

 which die or break off (Figs. 

 88 and 89); in the latter 

 figure the galleries of the 

 larvae have been exposed. 



The attack is indicated by discoloration and swelling- up of 

 the bark, and later on by its depression over the points of 

 injury, and by the brown wood-dust which is ejected from the 

 burrows, or has fallen to the ground. 



The beetle attacks and kills isolated stems along the banks 

 of streams where the localities are not too dry, and since 

 1830, it has been common near Tharand in Saxony. In 



Figs. 88 and 89. Larval burrows of 



C. lapathi, L., in Alder stems. 



(Natural size.') 



