144 The Galls of Essex; a Contribution to a
This species, like its con-
geners, emerges from the
gall in March or April.
Neuroterus laeviusculus,
Schenck (Fig. 40) [aga-
mous form of Spathe-
gaster albipes.]
Quercus . Robur, L.
Leaf. This small gall is
attached to the mid or

Fig. 40. Neuroterus laeviusculus.
side ribs of the leaf on
its under side. It is egg-
shaped or oval, smooth,'
hairless, yellow or brown-
ish, and often covered with
bright red or purplish
spots; when mature it is
about one-tenth or one-
eighth of an inch in length.
The young gall is enclosed

in a thin membrane, which

Fig. 41. Neuroterus ostreus.
splits lengthwise, and the
scar on the leaf-vein is readily observable after the fall of
the mature gall in early autumn. It is single-celled,
with a relatively large cavity; the gall-fly emerges there-
from in November or December. Neuroterus ostreus,
Hartig (Fig. 41) [agamous form of Spathegaster apri-
linus] .
Quercus Robur, L. Leaf and male flowers. The common
"oak currant" gall is a smooth, sappy, green (frequently
more or less red on the catkin specimens), translucent,
spherical gall of about the size of a large pea; it
occurs on the under side of the leaf (where it is con-
texturate with it above, exhibiting a well-defined, convex,
succulent swelling of the surface) and ou the catkins,
generally four or five specimens on a single leaf or
catkin. It has a single larva-cell, which is small; the
gall grows very quickly, and the gall-fly emerges therefrom