125 
in St Janus a and Hyde Paris. 
dispersion of the disease, by destroying the brood of larvae while 
yet in the tree. 
As soon as metamorphosis has taken place, as soon as the 
winged insect has made its appearance, the mischief for the en- 
suing year is done. Not only is time thus lost, and more trees 
inevitably destroyed, but the future eradication of the disease is 
rendered much more difficult. 
We may also derive another advantage from ascertaining the 
habitSgof that particular insect which causes the disease, and the 
season of its appearance ; for it is often thus possible, by timely 
measures, even in places where the perfect insect is prevalent, to 
prevent any deposition of eggs in such wood as may have re- 
mained sound. At all events, the devastation committed by 
these animals is at times so great, that it is clearly worth while 
to make experiments to obviate it ; although it is difficult to 
conceive how such experiments can ever be made philosophically 
by persons who do not in the first instance make themselves ac- 
quainted with the natural history of that particular species of 
destructive insect which may have occasioned the mischief. 
Of the evil which is mentioned above in general terms, St 
James’s and Hyde Parks afford us at present too many examples. 
The elm-trees in both, and particularly in St James’s Park, are 
rapidly disappearing, and unless decisive measures be soon taken 
to resist the progress of the contagion, we must not only expect 
every tree of this species to be destroyed in the Parks, but may 
have to regret the dissemination of the evil throughout the vici- 
nity of London. 
In St James’s Park, which has more particularly been subject 
to my examination, there are several species of beetle to be 
found attacking the elms. That species, however, which occa- 
sions all the havoc which we have now to lament in the Mall 
and Bird-Cage Walk, is the Hylesinus destructor of Fabricius, 
or Scolytus destructor of Latreille, an insect of which the history 
is briefly as follows. 
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 
