158 THE OAK GALLS AND GALL INSECTS
Inquilines. Synergus albipes, S. facialis (Htg.), and S. radiatus
(Mayr.)
Gall.
Appears on the leaves, causing irregular thickening. An
inner oval yellowish gall contains the larva. These galls twist
and distort the leaves, which in some cases do not mature at all.
They are often numerous, causing continuous swellings. They
often appear on young twigs, twisting them and causing them
to grow in a permanently bent condition.
Imago.
Colour: Black. Antennae: Dark, pale at base; Apex gradually thickened.
Thorax: Without sculpture, smooth. Abdomen: Black and shining. Legs;
Testaceous; coxae always, and femora sometimes, dark. Wings: Hyaline.
Account of Generation Cycle.
When the A. collaris galls mature, a year and a half elapses
before the insects emerge. This takes place at the end of
March or the beginning of April.
The eggs are laid in the rudimentary leaves at the centre of
the bud. These leaves are distorted and thickened by the
resulting A. curvator galls, which appear in May, the flies
emerging from them in June. These, after copulation, lay one
egg in each bud, the A. collaris galls appearing in September,
and sometimes in August. In October the gall falls to the
ground, but the flies do not emerge until March or April of the
second year.
OCCURRENCE IN EPPING FOREST.
Andricus collaris. Abundant. These galls do not always fall
to the ground when mature, but those that do not I have usually
found to be parasitised. First appearance noted, August 22nd.
Andricus curvator. Very plentiful. I have occasionally met
with this gall on the fruit stalk at the time when the acorn has
just begun to form. The stalk is then bent nearly double, and
much thickened. This gall, however, is usually found on the
leaf. First appearance noted, May 14th.
(16). Agamic Generation. VI. Andricus callidoma
(Thoms).
Inquilines. Synergus nervosus (Htg.) and S. vulgaris (Htg.)