THE JOURNAL 



OF THE 



BOARD OF AGRICULTURE. 



Vol. XVI. No. 6. 



SEPTEMBER, 1909. 



THE GENUS CHERMES IN ITS RELATION TO 

 FORESTRY. 



R. Stewart MacDougall, M.A., D.Sc. 



The genus Chermes of the family Aphides is one of great 

 interest in forestry, partly because of its complicated biology 

 and partly because of the damage done by the sucking insects 

 and the unsightly appearance of plants infested by them. 



Progress in real knowledge of the Chermes insects may be 

 said to date from 1887, when Blochmann noted the fact that 

 there was a migration of Chermes generations from the 

 Spruce to the Larch and back again. Dreyfus worked out 

 this life history independently, as did also Cholodkovsky. 

 More than anyone, Cholodkovsky has made this genus his 

 own with a work in 1889, a monograph in 1895 and 1896, a 

 further work in 1902, and one in 1907. Eckstein in 1890, in 

 Prussia, and Niisslin in 1903, in Bavaria, have both written 

 on the biology of the Chermes that are found on the genus 

 Abies. Burdon has recently,* in three articles in the Journal 

 of Economic Biology, given an account of his own observa- 

 tions and experiments, together with a resume of Cholod- 

 kovsky 's work on Chermes, thereby placing foresters and 

 biologists generally in Britain deeply in his debt. 



In the literature on Chermes and in the text-books there is 

 considerable confusion regarding the terminology, and in this 

 article I shall follow that of Cholodkovsky, adding a note 



* E. R. Burdon, M.A., F.L.S., in the Journal of Economic Biology, 1907, 

 Vol. II, rts. 1, 2, and 4. 



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