598 



Chermes sfrobi, Hartig., is frequently found on the bark of trunks 

 and branches of Pinus strobus ; the stem-mothers and galls of this 

 species are not known and the author is of opinion that it cannot 

 complete its full cycle of development in Europe. 



Besides the above species which occur in Europe and Russia, exotic 

 species are also dealt with. C abielis-piceae (C. himalayensis, 

 Stebbing), is regarded as a distinct species, near to C. (Aphrasthasia) 

 pectinafae, Cholod. With regard to C cooleyi, Gillette, (J. montana, 

 Gillette, C similis, Gillette, C. coloradensis, Gillette, C. pinifoliae, 

 Fitch, C abietis, Kalt., C lariciatus, Patch, C. consolidatus, Patch, 

 C. flocais, Patch, C. similis, Gillette, and C. ]nnicarticis,¥ itch, only 

 C. coolei/i, C. fiocciis, and C lariciatus can be regarded at present as 

 well-established, distinct species. 



All the described European species of Chermes can be divided 

 biologically into three groups : (1) Those breeding on firs and larches, 

 or 0)ily on firs or only on larches, viz : — C viridis and C abietis ; 

 C. viridanus and C. viridulus ; C strobilobius and C laqyponicus ; 

 (2) those breeding on firs and silver firs or only on silver firs, viz : — 

 C pecfiivitae, C. fiinitectus and C piceae ; and (3) those breeding on 

 firs and on trees of the genus Pinus, or only on firs, or only on pines 

 {C. sibiricus, C strobi, C pini and C piniodes). Thus fir trees connect 

 in some way the difEerent groups, but some of the species have freed 

 themselves from this connection and breed only on intermediate trees, 

 e.g. C. piceae, C- viridanus and C viridulus, while others have dispensed 

 with migi'ations and occur only on firs. The origin and importance 

 of migrations is discussed, and the author still holds to the hypothesis 

 he proposed in 1896, that the ancestral forms of Chermes lived only 

 on trees of the genus Picea and only on the bark, where they produced 

 sexual forms at the end of summer ; this yearly cycle gave way to a 

 two-yearly one, when, through some agency or other, such as wind, 

 the winged individuals were transported to other trees, and, in mixed 

 forests, to trees of some other genus ; in such forests the descendants 

 of these emigrants have had to adapt themselves to breeding on new 

 trees, though the following year the same causes may have brought 

 the sexuparae of these forms back to firs, where they gave birth to a 

 sexual generation. If the occurrence of sexual forms even of a single 

 species of Chermes on any other trees than firs should be discovered, 

 the author's theory will have to be revised. 



Enemies of Chermes include Chalcididae, although the author 

 himself has never discovered them attacking Chermes ; Syrphid 

 and other Dipterous larvae, such as those of Agromyza chermivora, 

 Kalt. ; Coccinellid larvae, especially of the genus Scymnus ; larvae of 

 Anthocoris. various Acarids, etc The larvae of some Tenthredinidae 

 and Lepidopterous caterpillars are casual enemies, which devour 

 individual Chermes together with the needles of Conifers. 



The damage done by Chermes consists of (1) the formation of galls, 

 followed by total destruction or deformation of the shoots, the most 

 injurious in this respect being those species which have no migration 

 and breed from year to year on the same trees ; (2) the sucking of 

 the bark, which is however less important, although C piceae var. 

 bouvieri and C funitectus are very injurious in this respect, the 

 latter chiefly to young trees ; and (3) sucking of the needles, which is 

 also of no great importance, except in the case of C funitectus. The 



