Biology Reference
In-Depth Information
Nematus melanaspis
Hartig (
995
)
syn.
N. maculiger
Cameron
Gregarious poplar sawfly
A generally common pest of poplar (
Populus
);
infestations also occur on birch (
Betula
) and willow
(
Salix
). Widely distributed throughout central and
northern Europe.
Nematus nigricornis
Lepeletier (
996
)
A minor pest of poplar (
Populus
), especially black
poplar (
P. nigra
), and willow (
Salix
). Widely distributed
in central and northern Europe.
DESCRIPTION
Adult:
6-8 mm long; head black and hairy; thorax
black, marked with red; abdomen mainly yellow, with a
black back; legs reddish.
Larva:
up to 18 mm long;
head black; body relatively plump and mainly whitish
green to pale yellowish green, with several shiny black
verrucae along the back and sides; thoracic legs mainly
black.
DESCRIPTION
Adult:
6-8 mm long; pale yellowish white, the thorax
and upper side of the abdomen mainly black; head
brownish, with a dark facial mark; antennae short; legs
mainly pale, the hind legs partly black.
Larva:
up to
21 mm long; head shiny black; body mainly light green
to dull green, with the first thoracic segment orange;
three black stripes along the back, a double series of
shiny, black verrucae along the sides and another series
of verrucae above the legs; anal plate black.
LIFE HISTORY
Adults occur in two main generations, from May to June
and from July to August. Eggs are deposited in the leaf
stalks of poplar or willow. The larvae feed gregariously
along the edges of leaves, typically lying with the top of
the abdomen curled downwards on one side of the leaf
blade. They occur from June to September, fully grown
individuals eventually pupating in cocoons formed in
the soil.
LIFE HISTORY
Adults occur from May to June and from July to
August. Eggs are then deposited along the major
veins on the underside of leaves of poplar. The larvae
feed gregariously from June onwards, members of
the second generation completing their development in
the autumn. Fully grown larvae pupate in the soil in
tough, brown cocoons.
DAMAGE
Larvae devour all but the major leaf veins, and infested
branches are significantly defoliated.
DAMAGE
Infested leaves are reduced to a network of veins, heavy
infestations affecting the appearance and vigour of host
plants.
995
996
995
Larva of gregarious poplar sawfly (
Nematus melanaspis
).
996
Larva of
Nematus nigricornis
.
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