CH. XIX.] OBNOXIOUS INSECTS. 269 



might have had to regret the dissemination of the 

 evil throughout the vicinity of London. The devas- 

 tation committed by these animals is at times so 

 great, that it is clearly worth while to make exper- 

 iments to obviate it, although it is difficult to con- 

 ceive how such experiments can ever be made phi- 

 losophically, by persons who do not, in the first in- 

 stance, make themselves acquainted with the nat- 

 ural history of that particular species of destructive 

 insect which may have occasioned the mischief. 



A small beetle, with its head rather covered with 

 hair, having a polished black thorax and brown 

 wing-cases, may be seen in numbers running over 

 the trunks of the elms from the end of March to the 

 first days of July, but principally about the end of 

 May or the commencement of June. It may be 

 seen to enter into holes, with which the bark ap- 

 pears perforated as though with a gimlet. It insin- 

 uates itself into these holes, or into the crevices of 

 the bark, for the purpose of depositing its eggs. On 

 stripping off a piece of the loose bark, we may easily, 

 at any season, understand how the barking of trees 

 is effected by these minute insects, for the surface 

 of the wood thus exposed presents to the view in- 

 numerable impressions. The middle or body of this 

 smgular impression marks the path of the perfect 

 female insect, while employed in laying her eggs, 

 which is to her, as to most other winged insects, the 

 immediate forerunner of death. From this tubular 

 path, however, in which she deposites her eggs, the 

 larvae hatched from these eggs, in the shape of lit- 

 tle white worms, proceed nearly at right angles, eat- 

 ing their way in parallel smaller tubes, which, lying 

 close to each other, effectually serve to separate the 

 bark from the tree. The larvae remain feeding in 

 the tree, generally between the bark and the wood, 

 throughout the winter season. About the com- 

 mencement of spring they assume the pupa or 

 nympha state, and, before the end of this season, the 



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