INSECTS INJURIOUS TO FOREST TREES. 173 



XIX. On Insects Injurious to Forest Trees, and their Destruction. 

 By Malcolm Dunn, Palace Gardens, Dalkeith.* 



Whether we look at our subject from a scientific or cultural 

 point of view, it is of the greatest importance to foresters and 

 others who have to do with the cultivation of trees and shrubs, 

 and the management of timber, to be able to distinguish readily 

 the cause of any injury they may suffer from, and to quickly 

 apply a remedy, if such be known. No doubt trees suffer from 

 many other causes beside the injuries inflicted upon them by 

 insects ; but when, at the present time, the attention of scientific 

 and practical men in other branches of rural industry is so 

 anxiously and laboriously directed towards finding out effective 

 remedies against the voracious attack of some of the worst insect 

 plagues that have harrassed cultivation in modern times, such as the 

 ravenous attack of the Colorado beetle (Doryphora decem-jmnctata) 

 on the potato in the United States of America, and the still more 

 fatal ravages of the vine aphis (Phylloxera vastatrix) in the vine- 

 yards of France and the south of Europe, I consider it an oppor- 

 tune time for the Society to take up the important subject before 

 us, and discuss it in an intelligent and practical manner, so that 

 some useful result may be obtained from the expression of the 

 various opinions of members present, the comparison of their notes 

 on the injuries inflicted by insects upon trees and shrubs which 

 have come under their notice, and the remedies they have applied 

 or can suggest. 



In order to open the subject for discussion, I will make a 

 few remarks upon some of the best known insects which pi*ey 

 upon and do most injury to trees and shrubs in this country, 

 as it would far exceed the time at our disposal to go into a minute 

 and detailed description of all the species of insects that infest, and 

 more or less injure our forests. 



The Ajyhidce or plant-louse family is perhaps the most uni- 

 versally distributed of all the pests that prey upon trees and the 

 vegetable kingdom generally, and the injury done by them is 

 incalculable, as there is not a tree or plant which appears to be 

 exempt from their attacks in one way or another. Their extraord- 

 inary powers of reproduction render them a terrible scourge to 

 forest trees in seasons favourable to their existence, and the rav- 



* Read at the Twenty- Third Annual General Meeting, 1st November 1S76. 

 VOL. VIII., PART II. M 



