152 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



it is by no means established that this damage is solely due to 

 the sucking of the C/iermcs. 



Drcyfusia Nii.sslini must be considered a dangerous enemy of 

 silver fir. Abies nordmanniana is the conifer chiefly attacked, 

 but the indigenous silver fir A. pectinata may be equally 

 seriously attacked. 



2. Relative Immunity of the Various Species of Conifers. 

 {a) Spruces. 



(i.) Genera Chermes, s. str., and Cnaphalodes. — Common 

 Norway spruce {Ficea excelsa) is the favourite spruce host of 

 the species of these genera, and if it is present in sufficient 

 number other spruces are not attacked. 



These species of Chermesidse, however, can attack practically 

 all spruces — Ficea orientalis (Link, and Carr.), F. alba (Link.), 

 F. nigra (Link.), F. sitchensis (Cam), F. morinda (Link.), F.polita 

 (Carr.), F. pungens (Engelm.), F. E?igelmanni (Engelm.). 

 Of the spruces used silviculturally in this country white 

 spruce {Ficea alba) and Menzies spruce [F. sitchensis) may be 

 fairly badly galled, but only when the supply of Norway spruce 

 {F. excelsa) fails. 



(ii.) Genera Dreyfusia and Fineus. — Dreyfusia Niisslini and 

 Pineus pini rarely successfully attack any spruce other than 

 Ficea orientalis, so that the other spruces may be considered 

 immune to these species. 



{b) Larches. 



European larch {Larix eitropcBa, D.C.) is the favourite host 

 of the species of the genera Chermes, s. str., and Cnaphalodes. 

 I have found the Colonici of these species on Japanese laxch 

 {Larix leptolepis, End.) and other larches, but they were not 

 numerous on these exotic species. Japanese larch appears to be 

 relatively immune to Chermesidse, at least in the presence of 

 numerous European larch. 



{c) Pines. 



(i.) Fineus pini.— The. favourite host of this species is the 

 Scots pine {Finns silvestris, L.), but it has been recorded from 

 practically all pines, including F. inontana (Duroi), F. banksiana 

 (Lambert), F. contorta (Douglas), F. insigfiis (Douglas), and 



