146 The Galls of Essex; a Contribution to a
Quercus Robur, L. Leaf. This inconspicuous blister-
gall occurs as a circular swelling of the leaf on both sides.
The mature gall is about
one-eighth of an inch
across, by about one-
twentieth thick, and is
yellow in colour, but is
green, like the leaf, when
immature; on the upper
side radiate striations are

Fig. 45. Spathegaster vesicatrix.
frequently noticeable. The
gall is mature in spring,
and the gall-fly emerges
therefrom in June. Spathe-
gaster vesicatrix, Schlech-
tendal. (Fig. 45).
Quercus Robur, L. Male
flowers. In May and June
we often notice, as it were,
small locks of sheep's wool
in the oak trees, where no
sheep could get. These
are the galls of A. ramuli.
The gall is really a hard,

woody, irregularly-shaped

Fig. 46. Andricus ramuli.
mass, consisting of many
confluent larva-cells; but its whole small surface is covered
with this thickly-matted, yellowish-white, woolly growth, so
that the mass is often as large as a walnut or small apple.
The gall is attached to a catkin ; it is mature in June, and is
many-celled, the gall-flies emerging therefrom in June and
July. Andricus ramuli, Linne. (Fig. 46.)
Quercus Robur, L. Male flowers. Small, oviform, rarely
almost spherical, smooth, but more or less deeply ribbed
longitudinally according to their stage of maturity, brown,
greenish-brown or reddish, succulent galls, occurring in some
numbers on a catkin-stem; they are mostly sessile, but
occasionally have a short footstalk, which rarely is found