THE SILVER FIR. 



477 



health of the individual it infests, by disfiguring- and des- 

 troying the leading shoots, but very frequently causes the 

 actual death of the tree by the absorption of its juices, 

 which constitute the food of these small but destructive 

 beings. 



This pest, so fatal to the Silver Fir, appears to have 

 been greatly on the increase, and to have spread widely 

 and generally throughout every district of the kingdom, 

 wherever that tree has been introduced, within the last 

 twenty or thirty years, for we do not find that its ravages 

 had been noticed, or at least that trees of this species had 

 suffered to any injurious extent, previously to this period. 

 This Eriosoma, unlike many of the Aphides and Coccidd? 

 found upon various species of the Abietina, never attacks 

 the leaves of the tree, but is always confined to the main 

 stem, and the under sides of the branches ; upon these 

 parts it appears when first seen, or at least when first 

 distinctly visible to the naked eye, in minute patches of 

 a pure white, which, when closely inspected, are seen 

 externally to be of a flocculent or cottony substance. On 

 removing this covering, which is an exudation from the 

 body of the insect, the creature itself and numerous 

 bunches of eggs become visible, as represented in our 

 magnified figures. 



These creatures, by the 

 extraordinary mode of pro- 

 pagation common to the 

 members of the family to 

 which they belong, increase 

 with a rapidity it is scarcely 

 possible to imagine : and in 



a very short time, where at first a few scattered indivi- 

 duals only were to be seen, the entire surface of the bole 



