Agriculture Reference
In-Depth Information
DESCRIPTION
Adult
2-3 mm long;
body
greenish and globu-
lar;
saltatory appendage
forked and well deve-
loped;
antennae
long and geniculate
(Fig.
179). Egg
0.3 mm in diameter, globular, whit-
ish-yellow.
Nymph
similar to adult but smaller.
ORDER DERMAPTERA (EARWIGS)
Family FORFICULIDAE
Forficula auricularia
L.
Common earwig
will destroy large numbers of aphids and other
pests.
BIOLOGY
Adult earwigs, reared during the summer or au-
tumn, overwinter in the soil and mate in the early
winter. In December or January, each mated fe-
male lays a batch of up to 100 eggs in an earthen
cell (brood chamber); the maternal female then
guards over the eggs and, later, the first-instar
nymphs before eventually emerging. Nymphs
developing from 'winter' eggs usually reach the
adult stage by the early summer, individuals pass-
ing through four nymphal instars. The maternal
females often deposit smaller batches of eggs in
May or June, and nymphs arising from these eggs
usually complete their development by the end of
September. In parts of continental Europe, there
may be three egg-laying periods annually. Ear-
wigs are nocturnal insects, and usually hide dur-
ing the daytime amongst curled leaves, under
loose bark and in other sheltered situations.
Earwigs are polyphagous insects, and often
cause damage to chrysanthemum, clematis,
dahlia and other herbaceous plants, including
potato. Damaged petals become ragged, spoiling
the appearance of ornamentals. Attacks on
leaves are unimportant but chewed buds may
die, resulting in blind shoots; most damage oc-
curs from June to September. Earwigs some-
times attack celery plants, to form brownish,
longitudinal grooves in the petioles; such
damage is distinguished from similar symptoms
of physiological disorders by the presence of
masses of black frass
(Plate la)
and tends to
occur most frequently on plants suffering from
boron deficiency. Earwigs may also shelter
beneath the sheaths of developing maize (and
sweet corn) cobs and then damage the kernels,
particularly at the tips of the cobs
(Plate lb).
In
orchards, earwigs often feed on ripening fruits
already damaged by mechanical or other means;
also, in black currant plantations, earwigs (which
often rest in the bushes) are frequent contami-
nants in trays of mechanically harvested fruit.
Although of some pest status, both outdoors and
in glasshouses, earwigs are also beneficial and
DESCRIPTION
Adult female
12-14 mm long, chestnut-brown;
posterior pincers
slightly curved (see Fig.
18a).
Adult male
similar in appearance to fe-
male but larger;
posterior pincers
strongly curved
(see Fig. 18b).
Egg
1.3 x 0.8mm, oval, pale
yellow.
Nymph
whitish or greyish to brown.
ORDER THYSANOPTERA (THRIPS)
Family AEOLOTHRIPIDAE
(banded thrips)
crops such as field bean, linseed and oilseed rape,
but is of little or no pest status. Second-instar
nymphs are at least partly predacious.
Aeolothrips intermedins
Bagnall
BIOLOGY
Adults occur from May to August, and nymphs
develop from July onwards. Fully grown nymphs
This generally common species is associated
with various members of the Asteraceae,
Brassicaceae, Fabaceae and Linaceae, including
