Rhagonycha elongata (Fallen, 1807)
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POLYPHAGA Emery, 1886
ELATEROIDEA Leach, 1815
CANTHARINAE Imhoff, 1856
CANTHARINI Imhoff, 1856
Rhagonycha Eschscholtz, 1830
This is a mostly central and Northern European species, it occurs continuously from the Pyrenees to Northern Italy and Ukraine and is known from various Balkan countries, to the north it extends to the UK and far above the Arctic Circle in Scandinavia. To the east it extends through Russia and into Siberia and Mongolia although it is not known whether this distribution is continuous. In the UK it is very local and scarce although adults tend to be common where they occur; it is known from the Scottish highlands south to the Grampians and there are modern records from Orkney, it is often represented on distribution maps by widespread records in England and Wales but these are now known to be in error and so older (pre-1979) records need to be treated with caution. The species occurs from lowland to lower mountain altitudes; in Northern Europe up to about 1500 m, and is it usually associated with wetlands, damp coniferous woodland, moorland and open boggy habitats although adults have sometimes been found to be abundant by old established hedgerows on agricultural borders. In the UK it is almost always associated with trees and shrubs in extensive pine woodland; adults often occur in the canopy of Scots Pine (Pinus sylvestris L.) although they visit also visit a range of flowers and may be common on vegetation beside moorland ponds etc. Adults occur over a short season from May until July or August; they consume on pollen and nectar of a wide range of flowers but are also predatory and will take other small insects and their early stages from foliage and flowers. Females oviposit in the ground and larvae emerge later in the summer. Larvae are terrestrial predators; they consume other small arthropods etc. and they are cold-tolerant, remaining active and developing through the winter. Pupation occurs in the soil during early spring and the first adults appear during May. Adults may be beaten or swept from foliage and flowers, they usually occur in numbers and are very distinctive although after feeding on pine flowers they often become covered in pollen and are not immediately obvious.
 Rhagonycha elongata 1 |
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6.0-7.5 mm. This is the only UK Rhagonycha with dark elytra and so should be easy to identify, but there are several superficially similar species of Cantharis and so it is important to identify the genus correctly by looking at the third tarsomere, which is not bilobed, and the claws, all of which are longitudinally split. In Cantharis the third tarsomere is bilobed and only the anterior claw is split. Body dark, shiny and finely pubescent, antennae dark with several basal segments pale, or at least paler, legs variable but usually dark with at least the tibiae and sometimes the tarsi pale brown. Head concave between convex and protruding eyes, temples long and curved, surface finely punctured and distinctly microsculptured, so appearing dull compared to the smooth pronotum. Terminal maxillary palpomere only weakly securiform. Pronotum transverse, broadest across slightly obtuse posterior angles and narrowed to a more-or-less rounded anterior margin, surface uneven, finely but not densely punctured throughout and with faint microsculpture (just visible at X20 and most obvious towards the anterior margin). Lateral and basal margins rather strongly raised. Elytra dilated from rounded shoulders to separately-rounded apical margins, surface very soft and so rarely evenly convex; finely punctured and rugose throughout, without distinct striae but usually with three long and one short longitudinal raised lines, the shorter one beginning under the raised humerus and merging with the lateral margin behind the middle.