150 THE OAK GALLS AND GALL INSECTS
Account of Generation Cycle.
The perfect insects emerge from the Dryophanta divisa galls,
and at once proceed to prick the buds. This happens in
October, near the end of the month, and at the beginning of
November. In the following May the galls of Dryophanta
verrucosus appear. They may develop on the leaf or from the
bud direct. From these galls the perfect insects of the sexual
generation emerge at the end of May, and lay their eggs in the
tenderest leaves, Dryophanta divisa galls appearing at the end of
July.
OCCURRENCE IN EPPING FOREST.
Dryophanta divisa. Not plentiful, though I found them in
some cases in numbers on the leaf. First appearance noted,
July 19th.
I was unable to obtain any specimens of Dryophanta
verrucosus.
(10.) Agamic Generation. IV. Dryophanta agama (Htg.)
Inquilines. Synergus pallicornis and S. albipes (Htg.)
Gall.
Shape: Circular. Found on the under-surface of the leaves
emanating from the leaf veins. Central hollow large; walls thin.
Colour: Pale yellow, but many have a pale pink or reddish tint,
becoming browner with age.
Imago.
Colour: black. Antennae: 12th antennae joint longer than broad; a
variable number of basal joints may be reddish. Thorax: More glabrous than
in preceding species. Abdomen; Black. Legs; Yellowish red, base of coxae
usually darker in colour.
There is no known sexual form, though it is probable that
another generation exists.
The galls are found towards the end of July and in August
on the veins at the back of the oak leaves. They can be easily
distinguished from D. divisa by their smaller size, rounder shape,
and larger larval cavity. The flies emerge in November.
OCCURRENCE IN EPPING FOREST.
This gall was not abundant but more frequently met with
than Dryophanta divisa. First appearance noted, August 10th.