Birch Shield Bug
(Elasmostethus interstinctus)
Class Insecta
Order Hemiptera
Sub order Heteroptera
Infraorder Pentatomomorpha
Superfamily Pentatomoidea
Family Acanthosomatidae
Genus Elasmostethus
Species Elasmostethus interstinctus (Linnaeus)
Shield bug and stink bug (or shieldbug and
stinkbug) are common names applied to various
insects of the Hemiptera order (the "true bugs"),
in the Heteroptera suborder. Shield bugs have
glands in their thorax between the first and
second pair of legs which produce a foul smelling
liquid. This liquid is used defensively to deter
potential predators and is sometimes released
when the bugs are handled carelessly. The stink
comes from aldehydes such as trans-2-octenal
(OCT) and trans-2-decenal (DEC), and is
chemically similar to pheromones. The nymphs,
similar to adults except smaller and without wings, also have stink glands.
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The Acanthosomatidae is a family in the order Hemiptera commonly known as shield bugs. They are characterised from related families in having only two tarsal segments.
The superfamily Pentatomoidea consists of generally shield-shaped true bugs. Other species that resemble shield bugs are found in the Coreoidea superfamily.
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The nymphs and adults have piercing mouthparts which most use to suck sap from plants, although some eat other insects. When they group in large numbers they can become significant pests.
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The birch bug has a holarctic range, occurring from Alaska and Canada to Asia and Europe (Thomas, 1991). The Birch Shieldbug is common and widespread on birch in Britain. Canadians and Americans usually refer to this species simply as the Birch Bug.
E. interstinctus is 8-10mm long, the size is that of many other shield bugs. The dorsal side is bright green shieldbug with red or orange-brown markings on the base of the pronotum and scutellum and along the inner margins of the wings. The amount of red varies from individual to individual. Usually the animals are darker (brownish red) in winter.
It can be separated from the rather similar Juniper Shieldbug by the length of the first antennal segments, which clearly extend beyond the front of the head in both adults and nymphs of this species. The ventral side is yellow-green, and the abdominal margins are yellow(Thomas, 1991). Preserved specimens may become tan.
E. interstinctus feeds mostly on Betula. It has also been recorded feeding on Juniperus (Juniper), Quercus (Oak), Ilex (Holly), and Vaccinium (Schaefer and Ahmad, 1987); Alnus (Alder), Fagus (Beech), and Populus (Aspen) (Thomas, 1991). Birch bugs have been collected on Salix (Willow) (Scudder, 1997).
The adults of this species appear in September and overwinter. Barnes et al. (1996) studied the overwintering biology of E. interstinctus in Fairbanks, Alaska, from which the following is sumarized. Bugs adults survive harsh winter conditions by their selection of hybernacula and by supercooling. By spending the winter under the snow in the upper layers of leaf litter, Birch Bugs escape the coldest winter temperatures and avoid contact with ice crystals. The ability to supercool without freezing improves through the winter, with adults freezing, on average, at -9.5º C in fall to -16.9º C in spring. Freezing is lethal and contact with ice causes freezing at higher temperatures.
Adults love low bushes, preferably in the sun shine. Larvae found on Birch mainly. The larvae are usually seen in July and August. The developing nymphs and adults are most often found on trees with an open aspect that develop catkins on which the bugs feed.
In southern Finland and Sweden, Mappes et al. (1996) observed that E. interstinctus lays eggs on the upper side of leaves and on the catkins of Betula (Birch) from early June to the middle August and that the nymphs feed in aggregations on catkins until they reach adulthood. Adults overwinter in leaf litter, then mate in the following spring.
Feeding and other inter-species relationships
Associated with Elasmostethus interstinctus
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is endoparasitoid host of larva Subclytia rotundiventris - a parasitoid fly (Diptera: Tachinidae) Allen, A.A., 1966 Belshaw, R., 1993
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Feeding and other inter-species relationships
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Subclytia rotundiventris is associated with:
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larva Cyphostethus tristriatus - a shield bug (Hemiptera: Acanthosomatidae) larva is endoparasitoid of Belshaw, R., 1993
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larva Elasmostethus interstinctus - Birch Shield Bug (Hemiptera: Acanthosomatidae) larva is endoparasitoid of Belshaw, R., 1993
Allen, A.A., 1966
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larva Elasmucha grisea - Parent Bug (Hemiptera: Acanthosomatidae) larva is endoparasitoid of Belshaw, R., 1993 [NHM]
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larva Piezodorus lituratus - Gorse Shieldbug (Hemiptera: Pentatomidae) larva is endoparasitoid of Belshaw, R., 1993
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Hawthorn Shield Bug
(Acanthosoma haemorrhoidale)
Widespread in England, Wales and Ireland and belonging to the order
Hemiptera.
In Britain the Shield Bugs are represented by four different families;
Cydnidae, Acanthosomatidae, Pentatomidae and Scutelleridae. Generally
they are a true bug with a green and chestnut-brown, flattish oval or
shield shaped behind the thorax (hence their common names), the
distinctly triangular shape and the bright green scutellum or shield. The
latter is surronded by a bold red triangle formed by the forewings and
the rear of the pronotum. and the fact that their antennae are comprised
of five elements each, It's wings are pale and membranous at the tip.
Like a beetle, it folds its wings across its back. Its young nymph is similar
in appearance but brownish bronze in colour without wings. It is most
commonly found on hedges.
Length 13mm to 16mm.
The Hawthorn Shield Bug is relatively easy to find and is a good example
of a typical 'Shield Bug'. It is to be found on a number of tree and shrub
species, often on hawthorn, after which, it is named. Shield bugs are
mainly phytophagous (feeding on plant sap), though a few are
carnivorous and may even be useful in controlling pests. They are often
called Stink-Bugs because they can produce a horrible smell. In the
adults the noxiously smelling fluid is produced by a pair of glands in the
thorax and released via a pair of pits on the metathorax, in the nymphs
there are 3 pairs of scent glands in the abdomen and the liquid is
released through special openings in between the 3/4, the 4/5 and the
5/6 abdominal segments. The scent does work though and is known to
repel certain vertebrate predators, in some species it will strongly stain
your fingers like iodine.
It favours hedgerows and woods. Autumn adults hibernate in crevices in
trees or under pieces of bark or in grass tussocks and emerge again
April-July. The eggs are laid on leaves in batches of up to 24, the
nymphs hatch shortly and look very much like miniature adults in
June-August.
Feeding and other inter-species relationships
Associated with Acanthosoma haemorrhoidale:
is endoparasitoid host of larva Lophosia fasciata - a parasitoid fly (Diptera:
Tachinidae) Allen, A.A., 1987 Belshaw, R., 1993
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Dutch Elm Disease (Ophiostoma ulmi)
Birch bark beetle
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5-6 mm. Emerging in May-June. Univoltine.
The egg gallery is single-shafted, vertical, up to 20 cm. The larval tunnels are packed densely. Lives under the bark of thinner stems or thicker branches of birch (Betula).
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