Biology Reference
In-Depth Information
Byctiscus populi
(Linnaeus)
Aspen leaf roller weevil
This smaller (5-6 mm long), green or reddish, black-
legged weevil (the underside is characteristically bluish
black) is associated mainly with young aspen (
Populus
tremula
) trees, causing similar damage to the previous
species. Infestations occur occasionally on ornamental
plants but are of little or no importance.
DESCRIPTION
Adult:
5.0-6.5 mm long; bright red to dark red, with the
head, antennae, legs, scutellum and underside of body
black.
Egg:
1.0-1.5 mm long; oval, yellow.
Larva:
head brownish yellow; body yellow to orange-yellow,
and strongly C-shaped.
LIFE HISTORY
Adults appear in May and are most commonly
associated with young oak trees. In June, mated females
deposit eggs singly or in small groups in the midrib of
expanded leaves. At the same time, they initiate larval
feeding shelters by severing the leaf blade on both sides
(cf.
Apoderus coryli
, p. 148) of the midrib at right-
angles to the main axis, about a third of the distance
from the base (the oviposition point being about 10 mm
beyond the line of cut). The freed parts of the leaf blade
on either side of the midrib then fold until their surfaces
meet, and finally roll up from the tip to produce a
characteristic pouch within which larval development
takes place. Larvae feed within their shelters for about
six weeks, the rolled leaf fragment eventually falling to
the ground. Larvae then overwinter and pupate in the
spring.
Deporaus betulae
(Linnaeus) (
311-312
)
Birch leaf roller weevil
An often common but minor pest of young birch
(
Betula
) trees; also associated with certain other
trees, including alder (
Alnus
), beech (
Fagus sylvatica
),
common hazel (
Corylus avellana
) and hornbeam
(
Carpinus betulus
). Present throughout Europe.
DESCRIPTION
Adult:
3-5 mm long; black, with rectangular, deeply
pitted elytra; hind femora of male greatly thickened.
Larva:
up to 7 mm long; whitish.
311
DAMAGE
The unusual larval shelters attract attention but damage
to infested trees is not important.
Byctiscus betulae
(Linnaeus)
syn.
B. betuleti
(Fabricius)
Poplar leaf roll weevil
A widespread but locally distributed weevil, associated
mainly with common hazel (
Corylus avellana
) and
poplar (
Populus
), but also attacking alder (
Alnus
),
birch (
Betula
), elm (
Ulmus
), ornamental pear (
Pyrus
calleryana
'Chanticleer') and willow (
Salix
). Eggs are
laid in leaf veins during late May or June, typically
several per leaf. The female also partly severs the leaf
stalks, the leaf blade then rolling into a pendulous,
cigar-like tube within which larval development takes
place. Fully grown larvae pupate in the ground, some
adults emerging in the autumn but others not until the
following spring. Infestations are sometimes noticed
on cultivated plants but are usually of only minor
importance. The adult weevils are 6-9 mm long, dark
blue, green or red, with distinctly metallic legs; males
possess a pair of characteristic, forwardly directed
spines on the thorax.
311
Female birch leaf roller weevil (
Deporaus betulae
).
312
312
Larval habitation of birch leaf roller weevil (
Deporaus
betulae
) on
Fagus
.
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