164 THE OAK GALLS AND GALL INSECTS
The gall appears in August or September, falling to the
ground in October before the larva is mature. The flies emerge
at the end of October, or even as late as November, and prick
the buds for oviposition. Sometimes the perfect insect does not
emerge until March of the following year.
Many parasitised galls remain on the leaves during the
winter, either on the ground or still attached to the tree.
Though I have been able to breed the fly, I have not
succeeded in carrying out any successful experiment with regard
to the generation cycle of this species.
Dr. Adler, who mentions this species as belonging to the
genus Neuroterus, but at the same time proposes to separate it
from that genus, gives Neuroterus aprilinus as the probable sexual
generation, in which view he is supported by Professor Mayr.
As mentioned in the case of Neuroterus aprilinus, other forms
are given by different authors as representing the sexual gene-
ration of this species.
OCCURRENCE IN EPPING FOREST.
Andricus ostreus. Very abundant. Although this gall usually
occurs on the back of the leaf, this is not always the case, and it
may occasionally be found on the front. As a rule it is situated
on the mid rib, but sometimes on the lateral veins. There may be
one or more galls on each leaf. I have sometimes found as
many as six.
There is a distinct mark or scar left on the leaf vein after
the gall has fallen, due to the two dried membranes, which were
originally present at the base of the gall on each side. First
appearance noted, August 14th.
(21). Agamic Form. XI. Andricus solitarius (Fonsc).
Iniquilines. Synergus vulgaris (Htg.), S. facialis (Htg.) and.
S. radiatus (Mayr).
Gall.
Spindle shaped and pointed, widest near the base. Green in
colour when young, reddish brown later. A fresh gall is covered
with ferruginous hair; this is subsequently worn off, the gall
becoming quite smooth and brown. The larval cavity is fairly
large and the walls comparatively thin. It is found both in the
terminal and axillary buds.