442 



The Genus Chermes. 



[sept., 



here and there which may serve as a guide to the names 

 given by other workers. Cholodkovsky, in his recent work, 

 enumerates eleven European species of Chermes, but to 

 declare how many of these will persist as absolutely true 

 species, and how many exist in Britain, will still require 

 • patient and prolonged research. 



The difficulties in this respect are due to a variety of 

 causes — the smallness of the insects, the varied characters 

 that are relied on for distinction, the microscopic differences 

 in these characters, the varying structure of the Chermes in 

 its different stages and generations, the complicated biology, 

 and the migration which may take place to a second or inter- 

 mediate host tree, with the added difficulty that in the same 

 generation we may have parallel series differing both in 

 habit and in structure. 



Apart from true specific structural differences, it is possible 

 to group the Chermes in Britain biologically according as 

 they are found (a) to make galls on the Spruce (Picea), (b) 

 to infest the needles and bark of the Larch (Larix), (c) to infest 

 the needles or bark of twigs and stems of Pines (Pinus) and 

 Silver Firs (Abies), 



The Distribution of Chermes in Britain. — Chermes galls 

 on the Spruce (Picea) are common all over the country. In 

 Scotland I know the gall-making Chermes from Inverness- 

 shire southwards, and the galls have been sent to me from 

 Hertford, Shropshire, Nottingham, Wiltshire, and Sussex. 



Chermes on Larch I have either taken or had sent to me 

 from Sutherlandshire to Wigton ; indeed, from Sutherland 

 southwards it can be found in every county. I have records 

 of its occurrence in North and South Wales, and in 

 Yorkshire, Norfolk, Lincoln, Shropshire, Bedford, Notting- 

 ham, Rutland, Sussex and Devon. My records also show 

 Chermes on Scots Pine (Pinus sylvestris) in Fife, Perth- 

 shire, Forfar, and Yorkshire; on Weymouth Pine (Pinus 

 Strobus) in Suffolk; on Abies pectinata in Aberdeen, Suther- 

 land, Perth, Dumfries, and Devon; on Abies Nordmanniana 

 in Aberdeen, Sutherland, Perth, and Midlothian ; and on 

 Abies nobilis in Perthshire and Fife. 



General Description. — As introductory to the detailed life 

 histories the following general statements may be helpful : — 



