Anomala dubia (Scopoli, 1763)
Dune Chafer
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POLYPHAGA Emery, 1886
SCARABAEOIDEA Latreille, 1802
ANOMALINI Streubel, 1839
ANOMALA Samouelle, 1819
A widespread and generally common lowland species occurring throughout Europe from France to the UK and southern Fennoscandia in the north and the northern Mediterranean to the south although it is absent from the southern-most extremes, and extending through Russia into Siberia to the east. Here it is essentially a coastal species although there are inland records from Hampshire, Surrey, Sussex and East Anglia; it is generally common from South Wales to Cumbria and around the coast of Suffolk and Norfolk but rare and sporadic elsewhere, including a few records from the east coast of Scotland but there has been a general decline, as there has across much of Europe, due to human disturbance. The typical habitat is open sandy or clay-sandy soils with patchy vegetation; adults occur from May until August and are active warm weather, flying or swarming on sunny days and warm evenings and often visiting flowers, they graze a wide range of foliage and have been recorded eating pine needles on the continent. Large populations may occasionally develop and in some continental areas it is an occasional pest of orchards and field crops. Mating occurs from late May or June and females dig down into the sand to oviposit, they usually choose areas of exposed sand clear of leaf-litter or other debris and may lay several batches of eggs. Larvae develop between 30 and 60 cm below the surface, they consume the roots of wild grasses as well as cereal crops and shrubs etc, and pass through three instars; in the autumn they dig deeper into the soil and overwinter in the second instar then resume feeding and complete their development the following spring, pupation occurs in a subterranean cell and this stage lasts between thirty and forty days. This two-year life-cycle is usual over most of the European range but under optimal ecological and nutritional conditions the species may be univoltine; an interesting discussion of this can be found HERE.
Two subspecies are generally accepted as valid; A. d. dubia (Scopoli, 1763) occurs throughout the European range, including the UK, while A. d. abchasica Motschulsky, 1854, which was formerly considered as a distinct species, is more eastern, occurring in Armenia, Azerbaijan, Georgia and Russia.
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11-15mm, A broadly elongate species; convex and almost continuous in outline and very variable in colour, from black or brown with a green to violet metallic lustre to entirely metallic blue, violet or green, continental specimens occur with the forebody dark and the elytra brown with or without a metallic lustre; some of these varieties predominate in certain areas and forms have been named but there is always a wide overlap and the designation of distinct forms or subspecies does not seem to be appropriate. Distinguished from our other chafers by the smoothly curved elytral margin, in Cetoniinae they are often indented behind the shoulder, and the form of the claws which are strongly asymmetrical; the inner pro- and meso-tarsal claws being wider and longitudinally split. Our only other member of the subfamily is readily identified by the form of the pronotum. Head smoothly convex and finely punctured, with relatively large and weakly convex eyes and evenly rounded anteriorly. Antennae nine –segmented, generally pale with the club extensively darkened. Pronotum widest across the base and evenly narrowed to a rounded anterior margin, surface extensively and quite strongly punctured, basal margin strongly sinuate. Scutellum large and triangular, rugose, densely punctured and coloured as the pronotum. Elytra broadest behind the middle and continuously rounded apically, generally with a wide and distinct impression laterally behind prominent shoulders. Elytral surface rugose and finely punctured throughout, striae variously impressed and often obliterated in places. UK specimens are generally metallic green, blue or violet throughout but the pronotal margins and elytra may be extensively pale brown.