Biology Reference
In-Depth Information
391
392
391
Galls of
Harmandia cavernosa
on leaf of
Populus tremula
.
392
Galls of aspen leaf gall midge (
Harmandia tremulae
).
393
Harmandia cavernosa
(Rübsaamen) (
391
)
Galls formed by this species commonly occur in pairs at
the base of the leaves of aspen (
Populus tremula
) and
white poplar (
P. alba
). The galls develop as light green
swellings (up to 5 mm across) on the underside of the
leaf blade, with a distinct opening through the upper
surface. Each gall contains a single yellowish-red larva,
which eventually escapes to pupate in the soil. Mature
galls are distinctly blackened; however, although very
noticeable, they cause little or no distortion of leaves.
Harmandia tremulae
(Winnertz) (
392
)
Aspen leaf gall midge
Leaves of aspen (
Populus tremula
) are often disfigured
by spherical, red to purplish-red galls induced by this
pest; they arise on the upper surface, each from a major
vein, but do not cause distortion. The galls (up to 4 mm
in diameter) develop from June onwards, reaching
maturity in August or September. There are usually
several galls per infested leaf, each containing a single
larva. Fully fed larvae vacate the galls in the autumn and
eventually pupate in the soil, adults appearing in the
spring. There is one generation annually.
393
Gall of beech hairy-pouch-gall midge (
Hartigiola
annulipes
).
Hartigiola annulipes
(Hartig) (
393
)
syn.
Hormomyia piligera
Loew, H.;
Pegobia
tornatella
(Bremi)
Beech hairy-pouch-gall midge
Beech (
Fagus sylvatica
) is commonly attacked by this
widespread gall midge. The adults, which occur from
mid-May to early June, insert eggs through the upper
epidermis of expanded leaves, generally close to the
midrib. In July, inner tissue of the leaf bursts through the
upper surface at each oviposition point to form
yellowish, hairy, cylindrical galls (
c
.5
enclosing a small (up to 3 mm long) white larva. The
galls eventually turn reddish brown and, in the late
summer, when mature, they break away from the leaf
and drop to the ground. Larvae overwinter within the
galls and pupate in the spring. An infested leaf might
bear several galls, sometimes as many as 50, but plant
growth is not affected.
×
3 mm), each
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