SAMPLE PLOT INVESTIGATIONS IN SCOTLAND. 171 



In all, over fifty sample plots for periodic study have been 

 established in Scotland since 1920. They are distributed from 

 Ross and Cromarty in the north to Kirkcudbright in the south, 

 and from Argyll in the west to Aberdeen in the east. Investi- 

 gations on the same lines are proceeding in England and Wales. 

 This investigation should throw new light on one of the most 

 important of forestry operations, and enable a forward step to 

 be made in the development of Scottish forestry. 



23, The Douglas Fir Chermes.^ 



Within recent years considerable interest has been aroused 

 among arboriculturists and silviculturists, especially in the South 

 of England, by the appearance of a chermes on the Douglas 

 fir. By many it was assumed to be identical with the larch 

 chermes C. strobilobius or C. viridis, but others looked on the 

 insect as one to be watched and studied. Finally, Professor 

 A. Henry submitted material to the Bureau of Entomology 

 in Washington, and was informed that this chermes was indeed 

 a newcomer and perhaps a dangerous one. Meanwhile, the 

 Forestry Commissioners had been interested in the question, 

 and they have now published the results of an investigation 

 into it made under their direction by Mr R. N. Chrystal, B.Sc. 



The problems which the Douglas fir chermes presented were 

 by no means simple. In the first place, even in America know- 

 ledge of the insect, which was determined as a species new to 

 science by the Russian authority Cholodkovsky, was incomplete. 

 Professor Gillette of Colorado first described the insect, which 

 he named Chermes cooleyi, as occurring on the Rocky Mountain 

 spruce. He also described what he believed to be a variety 

 of this species on the Douglas fir, which he named Chermes cooleyi 

 var. coweni. Subsequently Carl Borner placed Gillette's species 

 and its variety in a new genus Gillettea, and suggested that the 

 species and its variety were only different stages in the life- 



* " The Douglas Fir Chermes " {Chermes cooleyi), Bulletin No. 4, Forestry 

 Commission. Price, 2s. net. 



