Biology Reference
In-Depth Information
1043
Family
CYNIPIDAE
(gall wasps)
A group of small to tiny, mainly gall-forming wasps,
often with highly complex lifecycles. Many species are
associated with ornamental trees and shrubs.
Andricus kollari
(Hartig) (
1043-1044
)
Marble gall wasp
A common and often abundant pest of oak (
Quercus
),
especially English oak (
Q. robur
) and sessile oak
(
Q. petraea
); often of importance on young trees.
Widespread in Europe.
DESCRIPTION
Adult (asexual) female:
4-5 mm long; reddish yellow,
with gaster partly black; legs pale; wings hyaline but
tinged with red.
Larva:
plump, whitish.
1043
Galls of marble gall wasp (
Andricus kollari
).
1044
LIFE HISTORY
This cynipid forms large (up to 28 mm in diameter),
smooth, green to reddish, marble-like galls on young
oak trees. Each gall, which develops from the base of a
bud from late spring onwards, surrounds a small central
cavity and contains a single larva. The galls mature in
August or September. Adult (asexual) female wasps
either emerge during the autumn or early in the
following spring. These wasps deposit eggs in the
axillary buds of Turkish oak (
Quercus cerris
), to
produce an often overlooked bisexual generation of
larvae. Mated adult females from this early-spring
generation then initiate the familiar unisexual, summer
generation of marble galls. (In areas where Turkish oak
does not exist, the insect is represented merely by the
asexual generation.) Deserted marble galls, which soon
become woody, may persist for several years and are
often a common sight on scrub-oaks. The galls are
commonly invaded by parasitoids and inquilines, which
generally emerge in the spring through a series of small
exit holes; parasitized galls may also remain small and
become prematurely woody.
1044
Old galls of marble gall wasp (
Andricus kollari
).
DAMAGE
Infestations cause considerable distortion on young trees
and can reduce the marketability of nursery stock. The
galls are also disfiguring, particularly when numerous.
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