12
THE ESSEX NATURALIST.
bleeding." This, though not obvious externally, may be
sufficient to enable the insects to obtain a certain amount of
sap (fermented or not) from, the bottoms of the very deepest
cracks in the bark. At all events, I can see nothing else to
account for the regular autumnal congress of insects round this
particular tree-trunk.
I find the fact that this phenomenon is observable occa-
sionally in connection with particular trees in this district,
especially elms, is quite Well known among woodmen, hedgers,
and farm labourers. Several of these have told me that, in
the course of time, a tree thus affected always dies from it.
One particularly-observant and intelligent old man, who has
worked for me for six or seven years, and is now over eighty,
tells me that, some years ago, he knew of an, elm at Pryors,
about half a mile away, which died from this cause.
DISCUSSION.
In the course of the debate which followed the reading of this note,
Mr. Charles Nicholson, F.E.S., said:—
Mr. Christy having sent me in advance a copy of his note, I have
been enabled to look up references to similar occurrences.
Unfortunately, I have never had the good fortune to come across
a "bleeding" tree, so that I can offer no first-hand evidence on the
subject. The phenomenon is, however, well known to entomologists,
and many instances are recorded in the magazines; but they are
difficult to find just when wanted, and those quoted hereafter are the
only ones I have been able to trace so far.
The cause of the "bleeding" is undoubtedly, as a rule, injury
inflicted on the tree; and this is usually due to borings of the larvae of
the Goat-moth (Cossus ligniperda), as will be seen by the instances quoted
hereafter. The removal of branches and twigs, by pruning or otherwise,
during the growing season is also liable to cause bleeding; and it seems
to me highly probable that, in some cases (especially in such old trees
as those of which Mr. Christy writes), high wind might cause the trunk
or branches to split internally and so let out sap. Elm trees are par-
ticularly liable to shed their branches without any apparent cause and
might be damaged easily in that way. I understand that Mr. Christy's
tree does not appear to have been attacked by Cossus; nor has it lost
any branches. It seems possible, therefore, that an internal split in the
trunk may be the cause of the bleeding; and as the tree is old, this may
be difficult to heal, as the tree leans and is, therefore, possibly in an un-
healthy state.
Of the attractiveness to insects of exuding sap there is no doubt what-
ever. Coleoptera, Diptera, Hymenoptera, and Lepidoptera supply the
bulk of the visitors. The sap of most trees contains more or less sugar,
and easily ferments, thus forming alcohol, with the usual deplorable
results to the imbibing insects! Hence the "drowsy and semi-stupified"