Agriculture Reference
In-Depth Information
Hypera nigrirostris
(F.)
A clover leaf weevil
This species is associated mainly with clover. The
larvae typically form short slits in the stems
or burrow into the buds; the heads of attacked
plants may become distorted or young shoots
killed, but damage caused is rarely significant.
BIOLOGY
Overwintered adults are active in April and May,
and females deposit about 200 eggs over a period
of about 4 weeks. Eggs hatch in 2-3 weeks and
the larvae then burrow into the buds or stems.
Larvae usually feed for 3-4 weeks and then
pupate, each spinning a silken cocoon on the
plant or on the soil surface. New adults appear
1-2 weeks later. These young adults feed for a
short time and then seek sheltered sites in which
to overwinter.
Fig.
232 A clover leaf weevil,
Hvpera nigrirostris
(x!8).
DESCRIPTION
Adult
3-4 mm long, mainly blackish, partly
clothed in green, greenish-grey or brownish,
hair-like scales;
legs
red with dark femora
(Fig. 232). Larva
up to 5mm long;
body
yellowish-green.
the stems of plants. Each female deposits 600-
800 eggs over a period of several weeks, and the
eggs hatch 2-3 weeks after being laid. The larvae
feed within the stem for a few days and then
migrate to the shoot tips where they attack the
buds. They feed externally (this is unusual for
weevil larvae). Larvae are fully grown in 3 or
more weeks, passing through four instars. They
then pupate, each in a flimsy, yellowish-white,
net-like cocoon formed on the host plant, usually
on the underside of a leaf, or on the soil. Adults
emerge about 2 weeks later; they feed briefly
before seeking shelter in which to overwinter. In
the British Isles, this species is univoltine; how-
ever, in southern Europe, and in other favour-
able regions, there may be two generations
annually.
Hypera postica
(Gyllenhal)
A clover leaf weevil
Adults and larvae feed on the buds, leaves and
seeds of various members of the Fabaceae, espe-
cially lucerne and trefoils. Young foliage be-
comes tattered and riddled with irregular holes,
and flower buds are destroyed. The pest also
causes distortion, discoloration and death of
growing points. Attacks on seed crops are espe-
cially serious and usually most severe in dry
seasons; in the British Isles they occur mainly
in eastern England.
DESCRIPTION
Adult
4.5-5.5mm long and appear mainly grey-
ish-brown, with paired, dark, longitudinal stripes
extending dorsally down much of the body and
narrowing posteriorly on the elytra;
rostrum
relatively broad and about half as long as the
prothorax;
prothorax
often with a pale, narrow
BIOLOGY
Adults hibernate in hedgerows and other shel-
tered situations, reappearing in March and April.
After feeding for about 2 weeks, eggs are depos-
ited singly or in batches in small holes bitten into
