Mordellistena humeralis (Linnaeus, 1758)
POLYPHAGA Emery, 1886
TENEBRIONOIDEA Latreille, 1802
MORDELLINAE Latreille, 1802
MORDELLISTENINI Ermisch, 1941
Mordellistena Costa, A., 1854
Among the most widespread of the Palaearctic member of the genus, this species is generally common and often abundant from lowlands to low mountain altitudes; at least 1000m, throughout Europe, north to the Baltic coast and the UK and south to the northern borders of the Mediterranean, to the east it ranges through Mongolia and Siberia and is also present in Japan. Here it is locally common in England north to The Wash although it is generally absent from the West Country and most of Wales; typical habitats include deciduous woodland with plenty of trees in various stages of decay, hedgerows, old established parkland and wooded borders. Adults are active over a short season from the middle of June until the middle of August, they may occasionally be swept from foliage but will generally occur in warm weather on a variety of flowers, more especially various umbels but also on meadowsweet (Filipendula ulmaria (L.)), species of Galium L., Spirea L. and, at least on the continent, hawthorn (Crataegus Tourn.) and elder (Sambucus L.). Adults are easily sampled by tapping flowers into a bag but they ‘tumble’ very actively and fly readily and so some care is needed to secure them, they also occur at light and may be found at night resting on trunks or logs. On the continent larvae have been recorded developing among decaying white wood of oak (Quercus spp.), hornbeam (Carpinus L.), alder (Mill.) and hazel (Corylus L.). Locally in South Hertfordshire and South Buckinghamshire this species is sporadically common and often occurs with our other two pale brown members of the genus, M. variegata (Fabricius, 1798) and M. neuwaldeggiana (Panzer, 1796), they are superficially similar and usually difficult to separate in the field and so need to be examined critically, over the past decade or so the present species has been by far the most numerous while the others are generally sporadic and scarce.
3.0-5.5mm. very variable in colour but usually extensively pale with black eyes and the elytral apex and antennae to some extent darkened, in any case the elytral humeri are generally paler than the rest of the elytra. Very dark specimens have the head and underside much darker than the pronotum and base of the elytra, the pronotal disc to some extent darkened and the elytra extensively dark; entirely pale and entirely dark specimens are known on the continent. Entire dorsal surface with pale and very fine recumbent pubescence. Head curved and abruptly truncate across the base, the temples very short between the eyes and the raised basal margin which is visible at the posterior angle, eyes smoothly convex and cheeks strongly narrowed to a rounded clypeal margin. Palps entirely pale; the apical maxillary palpomere securiform in both sexes. Antennomeres 1-3 pale, the remainder brown or at least contrastingly darker and usually darker towards the apex, the second segment more robust and slightly longer than the third, the fourth segment as long and as broad as the fifth. Pronotum broadest in front of sharply-acute posterior angles (from above) and strongly narrowed to a short anterior margin, basal margin produced medially and straight or curved inside the posterior angles. Elytra with rounded shoulders, almost parallel-sided in the basal half and evenly narrowed to a continuously curved apical margin, without striae except for traces of a sutural stria towards the base, surface densely and very finely punctured and pubescent. Front and middle legs long and slender; the femora and tibiae narrow and unarmed; the tibiae weakly curved. Hind legs much more robust; the tibiae flattened and gradually expanded to a broadly-oblique apex, each with a long and sharp spur at the inner apical angle and the outer face with three incomplete transverse ridges; the apical ridge short and almost transverse, the others longer and more oblique. Tarsi 5-5-4, without any bilobed segments, the basal segment longer than the others, hind tarsi much more robust than the others. A key including our UK species can be found HERE.