CHERMESID^ IN RELATION TO BRITISH FORESTRY. 151 



{c) Pine. 



Of the two species of Pineus, Pineus pini chiefly attacks Scots 

 pine {Pi/ius silvestris), while Pineus strobi only attacks Weymouth 

 pine {Pinus strobus). 



(i.) Pineus pini. — The Colonici feed on in the crevices of the 

 bark during spring, summer, and autumn. The Colonici may 

 be so numerous as to whiten the bark with their " wool " 

 (Plate III. Fig. 5). If the attack is very severe the Colonici may 

 spread on to the needles and feed there. The Colonici alatce 

 feed on the needles for a short time. This species is frequently 

 very troublesome in forest nurseries. If such infected trees are 

 planted out on unfavourable areas, the check to the conifer may 

 give the insect a chance to do damage, but if they are planted 

 out on a favourable area the pines gradually clear of the Chermes. 



(ii.) Pineus strobi. — The damage done by this species on 

 Weymouth pine is similar to that done by Pineus pini on 

 common pine. 



On the whole the damage done by Chermesid?e to pine is 

 much less serious than that done to the other intermediate 

 hosts. 



{d) Silver Fir. 



(i.) Dreyfusia N'dsslini. — The numerous Colonici feed at the 

 bases of the needles on the branches of young and old trees and 

 on the trunks of young trees (Plate III. Fig. 6). The Sexuparae 

 and Progredientes feed on the needles, especially those of the 

 opening buds. As a result of this sucking the needles of the 

 opening buds remain stunted. Frequently they become curled 

 in a characteristic way (Plate III. Fig. 7). Later they lose their 

 chlorophyll and turn yellow ; such needles fall off" prematurely. 

 This defoliation is serious, as silver fir takes about eight years to 

 completely renew its needles. The greatest damage is done to 

 young trees ; but silver firs up to twenty-five years old may be 

 attacked and in a few years killed by this species of Chermesidge. 



(ii.) Dreyfusia picece. — This species occurs on practically all 

 silver firs. The Colonici feed in spring, summer, and autumn 

 principally in crevices of the bark of old silver firs. The forms 

 feeding on the needles do not appear to be common. This 

 species does little or no damage to any silver fir except Abies 

 tiobiiis. On this silver fir it is to be found feeding on the buds. 

 Frequently large swellings appear on the infected branches, but 



