Insects - Pests of Ornamental Trees, Shrubs and Flowers - page 393

1067

1066

1066 Spangle galls of oak leaf smooth-gall cynipid
( Neuroterus albipes ).

1067 Galls of oak leaf blister-gall cynipid ( Neuroterus
numismalis ).

Neuroterus albipes (Schenck) ( 1066 )
syn. N. laeviusculus Schenck
Oak leaf smooth-gall cynipid
Spangle galls formed on the leaves of oak ( Quercus ) by
this cynipid wasp are smooth, irregularly saucer-shaped
with a slight central knob, and vary from creamy white
to reddish. They develop from July to October, and
finally drop to the ground when about 4 mm in diameter.
The galls are usually present in relatively small
numbers, and sometimes occur in company with those
of the more abundant species N. quercusbaccarum .
Larvae of the bisexual generation develop within
so-called Schenck's galls, which occur on the margins
of leaves in May and June. These galls are oval ( c. 2 ×
1 mm), green and smooth, although slightly hairy when
young.

Neuroterus tricolor (Hartig)
syn. N. fumipennis Hartig
Oak leaf cup-gall cynipid
This wasp forms spangle galls on the underside of the
leaves of oak ( Quercus ) from July onwards. The galls
are yellowish green, 3 mm in diameter and button-like,
each with a slightly raised rim bearing reddish hairs, and
a slight but noticeable central elevation. The bisexual
generation develops in shiny, whitish, yellowish or
greenish, pea-like galls, each with a temporary coating
of reddish hairs; the hairs drop off when about 5 mm
long. These galls, each up to 6 mm in diameter, arise
from the midrib or major veins on the underside of
leaves during May and June; they often occur singly, but
may coalesce and cause noticeable distortion of infested
leaves.

Neuroterus numismalis (Geoffroy in
Fourcroy) ( 1067 )
syn. N. politus Hartig; N. vesicator
(Schlechtendal)
Oak leaf blister-gall cynipid
The very characteristic golden-brown galls formed by
this species, develop on the underside of the leaves of
oak ( Quercus ) from August onwards. The galls (known
as spangle galls) measure up to 3 mm across, and have
a distinct central pit and a dense silky covering of short
hairs. They often occur in very large numbers,
sometimes more than 1,000 appearing on a single leaf.
The galls also cause a distinct discoloration of the upper
surface of infested leaves. Larvae of the bisexual
generation occur in May and June, within greenish or
greyish, hemispherical, partly ribbed blister galls
( c. 3 mm across); these are formed on either side of
young leaves.