OF EPPING FOREST.
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the veins of the undersurface of the tender leaves. Not until
September do the galls of Trigonaspis renum appear, and they then
take about three weeks to mature, falling to the ground in
October. The galls turn brown when the larvae matures, the
perfect insects emerging during the winter, or not until the
second year.
OCCURRENCE IN EPPING FOREST.
Trigonaspis renum. Extremely common. First appearance
noted, September 22nd.
Trigonaspis crustalis. Very abundant. Commonly found on
young oak plants about a foot in height, in which case a gall
may be present in every bud both above and below ground.
In the case of an old pollard oak, where the adventitious
buds growing on the trunk were very numerous, I found the
galls so plentiful as to practically cover the whole of the bark
near the base of the tree. Although when situated on the trunk
the galls are usually to be found near the ground, I have
occasionally found them as much as from six to eight feet up the
trunk. The galls may appear from the leaf stalk, and in one
case I found a gall arising direct from a leaf. First appearance
noted, May 3rd.
From a typical example of the galls of this species growing
on a young oak plant which I supplied from Epping Forest, a
coloured model in wax has been made and exhibited at the
Natural History Museum, South Kensington.
Genus CYNIPS (Linnetus).
This genus contains only one British species, which is the
largest of our gall-making Cynipidae. It is easily distinguished
from the insects of any other genus by the presence on the
abdomen of a rich pubescence of a silky nature.
There is only one generation a year, which is agamic, no
males being known.
Although this genus includes only one British species, there
are eighteen known in Europe, all of which are very difficult to
separate as perfect insects. This gall, like that of Biorhiza
terminalis, remains on the tree for a considerable period.