333 
DESCRIPTION. 
The appearance of an infested tree is well known to people who 
are interested in arboriculture or sylviculture, for the white, cottony 
covering with which the insect protects itself is very conspicuous. 
It is usually most abundant on the undersides of the branches and 
in cracks and depressions in the bark; but occasionally it may 
appear in large patches covering a considerable part of the trunk. 
The insect itself is less familiar, for it is very small, and though 
visible to the naked eye, a lens or microscope is required to study 
it satisfactorily. 
The mature insect has a rounded form and yellow colour, and a 
sucking-tube composed of three parts. This tube is attached to 
the lower side of the insect and is inserted in the bark so as to act 
It settles down in a short time, loses its legs, and becomes 
permanently attached to the bark by its sucking-tube. 
REFERENCES. 
That the disease is not a new one is evident, for occasional 
references have been made to it for more than half a century. The 
earliest record we have found occurs in the “ Gardeners’ Chronicle” 
for January 30th, 1858, p. 71. In this reference to the disease (in 
an editorial reply to a correspondent), the insect is called Psylla 
fag, and it is stated that it is understood not to injure the beech, 
though it infests it largely. In the issue of the same journal for 
Jan. 7th, 1860, p. 8, the coccus is again referred to, though under 
the name of Psilonia nivea, Fries., [Beech-bark Fungus]. It is 
described as being not common, but occurring in great abundance 
if at all. 
The following article by Mr. R. G. Foggo in vol. vii of the 
“ Edinburgh Botanical Society’s Transactions” 1863, p. 334, serves 
to show that the Coccus-disease was prevalent at that date, that its 
distribution was probably similar to what it is at the present day, 
and that during the half-century which has elapsed, little knowledge 
has been gained of the actual relation between the growth of the 
Coccus and the health of the trees. 
“For two or three years preceding 1858 my attention was 
directed to a disease which had proved fatal to some very fine 
specimens of beech in a gentleman’s park in the county of Suffolk. 
“The trees in question were greatly valued by the proprietor as 
objects of ornament, and various means were tried to effect a cure, 
and if possible, to arrest the further progress of the disease, but 
without any beneficial result. The beech is one of the most 
accommodating trees as regards soil and situation and it was 
evident that the disease did not arise from any peculiarity in the 
soil, which consisted of sandy loam, with subsoil of chalk and 
vel. In hot dry seasons the trees suffered much from drought. 
I mention this fact because I have seen the same form of disease 
