Agrilus angustulus (Illiger, 1803)

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POLYPHAGA Emery, 1886

BUPRESTOIDEA Leach, 1815

BUPRESTIDAE Leach, 1815

AGRILINAE Laporte, 1835

AGRILINI Laporte, 1835

Agrilus Curtis, 1825

Widespread across Europe from the Mediterranean north to the UK, Denmark and into some southern provinces of Fennoscandia, this species is also present on most of the Mediterranean islands, across North Africa and Asia Minor and recorded sporadically around the Caspian Sea and eastern Russia. The subspecies bicoloratus Abeille de Perrin, 1893 is the predominant form on North Africa while the usual unicoloured form predominates across Europe and Asia, but both occur throughout the range. This is the most common member of the genus across Central and Northern Europe but it becomes more sporadic and local in the west, especially in Spain and Portugal. In the UK it is locally common across Southern and Central England, becoming more local and scarce in the West Country, Wales and further north to Yorkshire and, with the exception of Agrilus biguttatus (Fabricius, 1777), is generally our most common buprestid. Typical habitats are open broadleaf woodland and wooded parkland but they also occur in rural gardens and on trees in hedgerows and on commons etc. Hosts include a range of broadleaf trees, usually oaks (Quercus L.), less frequently beech (Fagus L.), hornbeam (Carpinus L.), hazel (Corylus L.) and alder (Alnus Mill.), and occasionally Horse Chestnut (Aesculus L.), Birch (Betula L.), elm (Ulmus L.), Walnut (Juglans L.) and ironwood (Ostrya Scop). Adults are active between May and August although earlier or later specimens occasionally occur, and peak in abundance during June. The species is univoltine with mating and larval development occurring in spring and summer. Eggs are usually inserted into bark on small branches of young trees although they often choose branches and twigs high up on older oaks and sometimes on fallen branches or logs, and larvae burrow beneath the bark feeding on phloem vessels (phloemophagous), their irregular borings are visible as swellings on the surface and these may girdle smaller branches which eventually die off. Larvae overwinter under bark and pupate in situ in the spring and adults emerge via typical D-shaped emergence holes. Adults are active on warm days, especially in bright sun, where they may be seen flying in numbers about trunks and fallen timber, they otherwise rest on foliage or flowers and are difficult to see although they can usually be beaten or swept. They tend to occur in numbers and large populations may build up over several years, in Northern Europe they are occasional pests of commercial woodland and may attack saplings and fresh regrowth, but such populations fluctuate widely as natural enemies e.g. Spathius rubidus (Rossi, 1794) (Hymenoptera: Brachonidae) increase in abundance.

Agrilus angustulus 1

Agrilus angustulus 1

Agrilus angustulus 2

Agrilus angustulus 2

Agrilus angustulus 3

Agrilus angustulus 3

Agrilus angustulus 4

Agrilus angustulus 4

Agrilus angustulus 5

Agrilus angustulus 5

4.0-6.5 mm. Very typical of the genus; elongate, sinuate in outline and metallic strongly metallic greenish, bluish green or bronzy but bright blue or green specimens are not uncommon. Head rather flat between large convex eyes, moderately strongly and densely punctured, these often forming oblique series, and with a weak median longitudinal impression on the vertex and frons. Antennae serrate from segment 6, these segments triangular and slightly convex across the basal margin, and the terminal segment sinuate across the apex. Pronotum transverse, broadest about the middle and strongly narrowed to rounded posterior angles, apical margin widely produced medially and the basal margin very strongly bisinuate, surface with strong transverse sculpture, longitudinally depressed medially and with latero-basal keels extending to about the middle. Prosternal process more or less parallel-sided between the coxae and the anterior lobe rather deeply incised medially. Elytra dilated behind the middle and narrowed to separately-rounded apical margins, surface randomly and densely punctured throughout, these sometimes forming obscure oblique patterns, especially towards the apex. Apical abdominal sternite excised medially. Legs long and slender; femora unarmed and tibiae without obvious apical spurs. Tarsi 5.segmented; two basal segments simple, the third bilobed and the fourth more strongly so, terminal segment long and slender. Claws smooth and strongly appendiculate. Males may be distinguished by the presence of two small tubercles towards the apical margin of the second sternite, the sexes may also be determined by subtle differences in antennal structure but this is best done by comparison. Easily recognized among our UK fauna by the form of the prosternal process and apical lobe, the long pronotal latero-basal ridges and emarginate apical abdominal sternite.