I909-] 



The Genus Chermes. 



45 i 



come to me from Fife, Perthshire, and Yorkshire, and the Colonist 

 stage on Weymouth Pine from Suffolk. 



Chermes whose Intermediate Host is Abies, 



Of the Chermes group where Picea is the primary host and 

 an Abies the intermediate host we certainly have representatives in 

 Britain. 



Two separate species are described, and a third mentioned by 

 Cholodkovsky. Colonists, Exiles, and sexuparce, found on Silver Fir 

 by Niisslin, and described by him in the literature as Chermes picece, 

 have been determined by Cholodkovsky as respective stages in the life 

 history of Chermes funitectus Dreyfus. 



This would indicate that in Europe we have at least two Chermes 

 species with the normal five generations, the life cycle taking two years. 

 The primary host is a Spruce, on which a gall is made of the strobilo- 

 bius type, and the intermediate host an Abies. I have unworked 

 material of the stages on the intermediate host Abies pectinata, and 

 the same on Abies Nordmanniana and Abies nobilis. 



The needles of the Abies may be deformed and curl up, the tufts 

 of wool attesting the presence of the insect are well marked, and in 

 the case of the bark the white patches are very characteristic. 



In order that examples of the different types of life history may be 

 complete, I name here Chermes viridanus Choi., described by Cholod- 

 kovsky, and mentioned by Burdon. This species is exceptional in its 

 behaviour, inasmuch as it lives entirely on the Larch, the hibernating 

 larvae becoming winged adults which lay eggs on the larch needles ; 

 the larvae from these eggs feed till the autumn, and in the next summer 

 after four moults the winged generation is reached again. 



Damage to the Various Trees. — 1. Spruce. — Here it is the 

 buds which are damaged. The greatest damage is where the 

 galls are of the strobilobius type, and of the viridis and 

 abietis type. On account of the galls, the normal branching 

 and growth are interfered with. Shoots that would in ordin- 

 ary circumstances have developed normally are either sup- 

 pressed, or, remaining weak, perish later on. Shoots that 

 perish may show a marked curvature, and may break later. 

 Besides the asymmetrical development, there is a loss of 

 green assimilative tissue. 



C. viridis and C. abietis galls may be found on grown 

 trees up to twenty years of age. Young plants especially are 

 attacked, particularly if growing in unsuitable places. 

 Chermes strobilobius is not found so commonly on grown 

 plants. Spruce unfavourably situated, or weakened by frost 

 or by the injury of animals, may suffer severely, owing to a 

 great formation of galls. Fortunately, in connection with the 



