144
THE OAK GALLS AND GALL INSECTS
backs of the tender leaves, causing the Neuroterus fumipennis galls
to make their appearance in August or at the end of July.
OCCURRENCE IN EPPING FOREST.
Neuroterus fumipennis was very abundant. I have occasionally
found this gall, together with Neuroterus lenticularis, laeviusculus,
and numismalis, Andricus ostreus and Trigonaspis renum, all on the
back of the same leaf. First appearance noted July 29th,
Neuroterus tricolor was much less plentiful, and I only obtained a
few specimens. These galls when old often shed their hairs
and assume a brown dried-up appearance, exactly similar to an
old form of N. baccarum. The hairs, however, may remain on
the gall after it has dried up. I found this gall on May 30th.
(5). V. Neuroterus schlechtendali (Mayr.)
Gall.
Appears on the catkin of the Oak in May forming a swelling
in the connective or upper part of the filament of the stamen on
each side of which are the anther lobes. This swelling is smooth,
greenish-white in colour, with sometimes a tinge of pink,
becoming brown with age. The anther lobes are thrust up by the
swollen connective, forming what look like two flattened keels
extending on each side of the gall from just below the middle
to the apex.
The galls appear in May, but the life history of the insect has
not been fully worked out, as the gall is uncommon; the
perfect insects, however, emerge in July of the second year.4
Imago.
I have not succeeded in breeding any perfect insects from
these galls,
This species is said by some authors to be the agamic form
of Neuroterus aprilinus, but the generation cycle has not yet been
fully determined. I have been unable to breed any flies from the
galls that I obtained in the spring, and if they appear in July it
seems probable that this may be a sexual, and not an agamic
form.
OCCURRENCE IN EPPING FOREST.
I found Neuroterus schlechtendali galls on two trees only, a
number of galls being present on each catkin. They appeared
4 Alternating Generations. Adler and Straton.