Biology Reference
In-Depth Information
Family
CECIDOMYIIDAE
(gall midges)
Infestations are sometimes found on the foliage of
young trees in nurseries or amenity areas. The larvae
(up to 3 mm long) are whitish at first but later become
bright yellow; they develop singly, from June to early
August, eventually escaping through a small hole in the
side of the gall and dropping to the ground to pupate in
the soil. There is one generation annually.
Minute to small, delicate flies with moniliform flagellar
antennal segments, broad and often hairy wings (the
venation much reduced), long, thin legs and prominent
genitalia; adults are poor fliers and dispersal is often
wind-assisted. The larvae are short, narrowed at both
ends, and have a small, inconspicuous head; they
usually possess a sternal spatula ('anchor process' or
'breast-bone'), which is often of characteristic shape for
the genus or species.
Arnoldiola quercus (
Binnie) (
371
)
Oak terminal-shoot gall midge
Associated with oak (
Quercus
), infestations causing the
death of terminal shoots. The whitish larvae (up to
3 mm long) feed gregariously amongst the unfurling
leaves, infested tissue failing to open and eventually
turning black. There are usually two generations
annually, infestations coinciding with the development
of new leaf growth in the spring and summer. Attacks
are of little or no importance on mature trees, but they
can affect the growth of shoots on young trees and are
of some significance on nursery stock.
Anisostephus betulinum
(Kieffer) (
369-370
)
Birch leaf gall midge
A widespread species associated with birch, including
downy birch (
Betula pubescens
) and silver birch
(
B. pendula
). The larvae feed in distinctive galls formed
on the leaves, the galls developing as yellowish-red to
maroon pustules visible from above and from below.
Contarinia acerplicans
(Kieffer) (
372-373
)
Sycamore leaf-roll gall midge
This widely distributed European midge infests
sycamore (
Acer pseudoplatanus
), the larvae developing
gregariously within reddish marginal leaf-roll galls.
Galls might also develop on the leaves as elongate
folds; these are typically glabrous and shiny above and
hairy below, affected leaves often being considerably
distorted. The galls, which eventually turn black, first
appear on the young leaves in May. Fully fed larvae,
which are whitish and about 2 mm long, eventually
vacate the galls and drop to the ground to pupate in the
soil. There are two generations annually. Although
infestations sometimes occur on young ornamentals and
specimen trees, they do not cause significant damage.
369
369
Galls of birch leaf gall midge (
Anisostephus betulinum
).
370
371
370
Larva of birch leaf gall midge (
Anisostephus betulinum
).
371
Oak terminal-shoot gall midge (
Arnoldiola quercus
)
damage to young shoot of
Quercus
.
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