142 THE OAK GALLS AND GALL INSECTS
(3.) Agamic Generation. III. Neuroterus numismatis
(Ol.). Inquiline, Synergus tscheki (Mayr.)
Gall.
Appears on the back of the oak leaf, numbers being found on
one leaf. Commonly known as the "button gall." (Diameter
2 mm). Colour: Brown. Shape: Round, resembling buttons
made of a light brownish silk with a more or less deep depression
in the centre.
Imago.
Colour: Black. Antennae: Brownish black, may be a little lighter in
colour at the base. Thorax: Dull. Mesonotum shining. Legs: Variable.
Usually brownish yellow in colour. Wings: Hyaline.
(3.) Sexual Generation. IIIa. Neuroterus vesicatrix
(Schltal).
Gall.
Appears imbedded in the leaf substance. (Diameter 2-3
mm). Colour: Greenish. Shape: Circular, slightly bulging the
leaf surface. Centre somewhat raised, with rays running from it
to the margin.
Imago.
Colour: Black. Antennae: Brownish 2-3 basal joints yellow. Thorax:
Messonotum and scutellum smooth and shining. Parapsidal furrows usually
wanting. Legs: Yellow. Coxae and bases of femora dark. Wings: Hyaline.
End of 1st cubital cellule slightly clouded.
Account of Generation Cycle.
When the galls of N. numismatis drop to the ground,
development continues in the dampness thus afforded. The
insects emerge from them about the end of March. The indivi-
duals of this, the agamic generation, proceed at once to oviposit
in the buds, the resulting gall, N. vesicatrix, appearing in the
leaf in May. From these galls the sexual generation of insects
appears in June, the eggs being laid on the under-surface of the
tender leaves. In three or four weeks the galls of N. numismatis
appear.
OCCURRENCE IN EPPING FOREST.
Neuroterus numismatis was exceedingly plentiful, quite as much
so as N. lenticularis, the backs of the leaves often being entirely
covered. First appearance noted August 12th. Neuroterus
vesicatrix was not so common, the first specimen I met with