Amphimallon Latreille, 1825
Amphimallon is a genus of about 60 species of Western Palaearctic chafers, among the wider Rhizotrogini Burmeister, 1855, which includes more than 1400 species and occurs worldwide with the exception of Australasia, it is characterized by the 9-segmented antennae which, as with most other genera within the tribe, are sexually dimorphic with the male lamellae being longer than those of the female. In appearance they are typical of most of the tribe. The head is convex and smooth with at most incomplete or abbreviated carinae, rather strongly and densely punctured and pubescent and with large and convex eyes. The pronotum is finely to coarsely and densely punctured and microscopically reticulate although this may be very weak, and is usually clothed with erect, short to very long pubescence which may be sparse or moderately dense. The lateral margins are usually strongly bordered and there are sometimes small teeth or series of teeth. In all cases the meso- and metasternum are covered with long pubescence and the abdomen usually has shorter and sparser pubescence. The elytra usually have longitudinal ridges or sulci and often longitudinal lines of fine punctures and in most they are variously pubescent although glabrous and almost smooth forms exist. In all cases both sexes are fully-winged and in most the legs are sexually dimorphic with the female having various fossorial adaptations. The genus is restricted to the Palaearctic region, extending from the Iberian Peninsula to Greece and the Caucasus and into Central Asia and Siberia, and north to the UK and Fennoscandia. A single species, A. majale (Razoumowsky, 1789), has become widespread in the United States following accidental introductions from Western Europe. Typical of the subfamily as a whole they have white C-shaped fleshy larvae that feed on the roots of a very wide range of woody and herbaceous plants, and because the life-cycle may extend over two or several years very large populations may appear and so several species have become occasional serious agricultural or horticultural pests. Many species occur in grassland, scrub or agricultural habitats, especially on sandy or well-drained soils and in parkland and woodland margins. About 40 species occur in Europe and two extend to the UK. The only genus likely to be confused with Amphimallon is Melolontha but the two are readily separated:
-Smaller; 14-20mm. Antennal club with 3 segments. Abdomen without well-defined patches of white pubescence laterally.
-Larger; 20-30mm. Antennal club with more than 3 segments. Abdomen with well-defined patches of white pubescence laterally.
The two British species of Amphimallon differ as follows:
-14.20mm. Long pubescence on the pygidium and elytral apices as long as that on the pronotum. Elytra pale sandy brown. Antennal club dimorphic; lamellae in the male 2-3mm, in the female around 1mm.
-14-17mm. Long pubescence on the pygidium and elytral apices much shorter than that on the pronotum. Elytra darker reddish-brown. Antennal club dimorphic; lamellae in male around 1.5mm, in the female around 1.2mm.
Amphimallon solstitiale (Linnaeus, 1758)
This Western Palaearctic species occurs sporadically across western and southern Europe from Spain to the Balkans, reaching north to the UK and east into Russia but is absent from many central and northern areas, it is also present regionally as at least 6 subspecies. Here it occurs across southern England and Wales, including Anglesey, north to South Yorkshire and Lancashire, it is generally more common in coastal areas and, despite a general decline throughout its European range in recent decades, remains locally common or even abundant in many areas of the UK. Adults have a brief season, generally during June and July and often first appear close to the summer solstice, they are primarily crepuscular or nocturnal and may be observed in flight swarming around trees and shrubs or even buildings in nuptial flights and they often fly again during the early dawn. They are strongly attracted to light and will enter windows or alight on shop windows and so are often seen resting during the day. The typical habitats are wooded pasture, parkland and gardens where they rest during the day among foliage or on high branches, occasionally browsing foliage and buds of a wide range of deciduous trees. Following a period of feeding, females mate and oviposit into the soil where the larvae will feed on the roots of a range of plants, typically herbaceous grasses and they occasionally damage turf and may be pests of various soft fruits but they generally occur in small numbers and damage is slight compared with that occasionally caused by the cockchafer. Oviposition continues into July and the first larvae appear in late June, they usually develop over 2 years and when fully-grown, in late spring, they measure about 30mm and are creamy-white with yellowish brown head and appendages. Pupation occurs in a subterranean cell in early June and adults emerge after about 2 weeks.
14-20mm. This very distinctive species will soon become familiar but might be mistakes for the cockchafer; it is smaller, has a 3-segmented antennal club and lacks the lateral triangular white abdominal markings. The entire dorsal surface is pale sandy or olive-brown, turning darker in preserved specimens. The head is convex and densely punctured across the vertex, the clypeus has a raised border, the labrum is emarginate and the eyes are large and convex. Pronotum transverse; subparallel in the basal half and evenly rounded anteriorly, basal margin widely sinuate and posterior angles perpendicular, all margins strongly bordered. Pronotal pubescence fine and dense, especially towards the lateral margins. Pronotum large and densely punctured. Elytra finely and densely punctured, each with 2-4 incomplete raised longitudinal ridges alternating with 4 or 5 impressed striae. Dorsal pubescence creamy-yellow, long and erect, denser on the base of the elytra and pronotal margins. Legs long and robust, the pro-tibiae sexually dimorphic; in the female fossorial with 2 strong teeth on the outer margin, in both sexes the apex is produced into a long external spur. Meso- and meta-tibia with strong spines on outer margin in the female, male meta-tibiae with much smaller spines. Tarsi 5-segmented and simple, claws with a strong basal tooth.
Amphimallon fallenii (Gyllenhal, 1817)
This is a very local and generally rare central and northern European species with records from Germany, Denmark, Sweden and the U.K. There seems to have been a general, long-term decline in the UK and many former populations have disappeared e.g. it was last recorded from Cornwall in 1800, Devon in 1918 and Berkshire in 1904. Modern records include Dorset in 1996 and East Sussex in 2008 and it appears to be stable in several southern Welsh coastal localities, especially Pembrokeshire and Caernarvonshire but also more generally around the Welsh coast including Anglesey. The typical habitat in the UK is open, naturally grazed grassland and downland, especially near the coast e.g. along cliff tops with healthy rabbit populations. Adults occur from June to August and are most often seen around mid-day in warm weather, often in flight above the grass. Larvae develop in the soil, feeding upon the roots of grasses and other plants.
In appearance these are much the same as A. solstitiale but are generally darker, on average a little smaller, 14-17mm, and have the apical pubescence shorter when compared with that on the pronotum.