140 THE OAK GALLS AND GALL INSECTS
(1.) Sexual Generation. Ia. Neuroterus baccarum (Linn.)
Inquilines. Synergus facialis (Htg.) S. radiatus (Mayr.) S. albipes
(Htg.)
Gall.
Grows through the leaf or appears on the ♂ catkin. Colour:
Yellowish green, green and red or entirely red. Shape:
Globular. Soft and sappy. (Diameter 3-5 mm.)
Imago.
Colour: Black. Antennae: Brownish, 2-5 basal joints yellow; in the
♂ 15-jointed, in the ♀ 14-jointed. Thorax: Dull and rough; scutellum
wrinkled. Abdomen: Distinctly pedunculate. Ovipositor: Short. Legs:
Yellow, coxae entirely black or only at the base. Wings: Hyaline, broader
towards the apex, longer than the body; first cubital cellule clouded.
Account of Generation Cycle.
The Neuroterus lenticularis galls fall to the ground in September
and October, dampness being necessary to enable them to reach
maturity. They may be found in the winter in a swollen
condition, either separated from, or still adhering to, the leaf.
The insects emerge from these galls in April and sometimes
in May. This is the asexual brood, comprising females only, and
these immediately proceed to lay their eggs in the oak buds.
The resulting galls, N. baccarum, appear in May or the beginning
of June, the insects emerging from them at about the middle of
the month. The reason for this rapid maturity is to be found in
the soft and sappy condition of the galls, which are liable soon
to dry up. This being the sexual generation, oviposition takes
place only after copulation, and the eggs are laid in the backs of
the leaves at about the end of June. In three weeks galls appear
on the under-surface of the leaves. These are N. lenticularis galls.
Unless parasitised, the N. baccarum galls shrivel up soon after
the insects have emerged; these insects only lay their eggs on
the young and tender leaves.
OCCURRENCE IN EPPING FOREST.
I found Neuroterus lenticularis galls very common. First
appearance noted, July 19th. Neuroterus baccarum. Abundant.
Leaf and catkin galls both plentiful. In many cases I found
two or three galls amalgamated. First appearance noted
May 10th.
(2.) Agamic Generation. II. Neuroterus laeviusculis
(Schenck). Inquilines. Synergus tscheki (Mayr.)