Mordella Linnaeus, 1758
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POLYPHAGA Emery, 1886
TENEBRIONOIDEA Latreille, 1802
MORDELLINAE Latreille, 1802
MORDELLINI Latreille, 1802
M. holomelaena Apfelbeck, 1914
M. leucaspis Küster, 1849
This is a huge and cosmopolitan genus of more than 500 species, the greatest diversity is in tropical and subtropical regions and relatively few extend into northern temperate areas e.g. 24 are recorded from the Nearctic region and only 19 from Europe. The biology of the group is only poorly known but most develop in herbaceous stems or among decaying wood, adults occur over a short season in the summer and in temperate regions they are thought to be univoltine. Sampling usually involves searching flowers during warm weather, especially various umbels or Rosaceae, where the adults feed on pollen or beating or sweeping trees and shrubs, they fly well and many species have been recorded at light. Only 2 species have been recorded in the UK but there has been confusion over naming in the past and so other names will be found in the literature, the group was reviewed by Batten (1986) who provided much interesting information but more recent works should be referred to; keys to our UK species can be found HERE but for more critical work the link below should be explored. The genus can be identified by the form of the hind tibiae which have small tubercles, but lack ridges, on the outer face near the apex, the basal antennomeres are narrow compared to those following (in many exotic species they are strongly clubbed or serrate) and most species are entirely dark grey or black.
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M. holomelaena Apfelbeck, 1914
This very widespread though generally rare Palaearctic species occurs sporadically throughout Europe north to the UK and southern provinces of Fennoscandia end extends to the far east of Russia and Japan. Here it is very local and rare in the south of England from Kent to Hampshire and there are a few scattered records from Somerset, Gloucestershire, Herefordshire, Huntingdonshire and Lancashire although older records must be treated with caution as it was formerly confused in the UK with other species; it has been recorded from about 20 English localities but from only 4 of these since 1990. Adults are active over a short season from June to August; they are thermophilic and have been recorded from a wide range of flowers which they visit to feed on pollen, typically in open deciduous woodland but also on calcareous grassland. Little is known of the biology but the larvae are known to develop in decaying hardwoods and adults have been recorded from under bark.
6.5-8.0mm. Body entirely black, appendages black to dark brown, dorsal surface with dense short pubescence throughout. Base of head evenly curved to the posterior margins of the eyes, vertex and frons evenly convex, eyes weakly convex and finely pubescent; occupying most of the lateral margin, cheeks converging to a produced frontoclypeal area and the anterior margin of the labrum broad and slightly sinuate. Antennae inserted laterally in front of the eyes, the 2 basal segments short and near parallel-sided, 3 & 4 elongate and gradually broadened from a narrow base, 5-7 much broader throughout and 8-10 weakly serrate, the terminal segment rounded apically. Pronotum almost semi-circular (from above), broadest in front of rounded posterior angles and strongly sinuate across the base. Scutellum triangular, slightly sinuate laterally and rounded apically. Elytra gently curved laterally and narrowing from before the middle to separately curved apical margins, surface smooth but for a weakly raised and narrow sutural ridge, finely and densely punctured and pubescent throughout. Pygidium rather abruptly narrowed beyond the middle (view from directly above).Front and middle legs long and narrow, the tibiae with only a very fine spur on the inner apical angle, segments 3 and 4 of the front tarsi short; the fourth almost quadrate and distinctly emarginate across the apex. Hind legs long and robust, the tibiae with a long stout spur before the apical margin and lacking a dorsal ridge although often with an irregular row of granules, laterally with a groove parallel to the apical margin but lacking the series of transverse grooves seen in many genera. All claws with a series of fine teeth along the inner margin. Males can be determined by the almost circular second maxillary palpomere.
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M. leucaspis Küster, 1849
This is a more southern species in Europe, the nominate subspecies is widespread though local from Spain to Greece and extends sporadically into Central Europe but is generally absent from the Baltic States and Fennoscandia, and another subspecies M. l. bicolorpilosa Horak, 1985 is endemic to Crete. Its inclusion in the UK list is based on two very old records, from Wiltshire and Herefordshire, and a single record from Dorset during the 1980s. Very little is known of the biology of this species, on the continent adults appear during June and July on a range of flowers, mostly umbellifers but also e.g. spirea (Spirea L.) and spurges (Euphorbis L.), in open and warm wooded situations.
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9.0-10.5mm. Very similar to the previous species but differing in habitus; here the elytra are straight or even slightly concave in outline and taper more evenly from the base to the apex, the terminal maxillary palpomere is broader, the pygidium is more slender and evenly narrowed throughout its length and the third and fourth pro-tarsomeres are slightly elongate. Males may be distinguished by the partly pale front legs. Critical identification depends upon subtle characters, including the form of the aedeagus, and a detailed key (in German but which translates well with Google) can be found HERE.