Timarcha tenebricosa (Fabricius, 1775)

Lesser Bloody-nosed Beetle

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POLYPHAGA Emery, 1886

CHRYSOMELOIDEA Latreille, 1802

CHRYSOMELIDAE Latreille, 1802

CHRYSOMELINAE Latreille, 1802

TIMARCHINI Motschulsky, 1860

TIMARCHA Samouelle, 1819

This western Palaearctic species is locally common though sporadic across Europe from Spain to Greece and Ukraine in the south and north to the UK and southern Sweden, the eastern Baltic countries and the Russian Federation; here it occurs across southern and central England, including the Isle of Wight, to the north of Yorkshire though is generally absent from the West Country and Wales. It is generally a lowland species though adults have been recorded up to 1200m in Bulgaria. Typical habitats are open sites, often on calcareous grassland slopes exposed to the sun, but also more generally in grassland, heaths and moorland, forest and pasture margins, sandy grassland and dune slacks at the coast and marginal situations beside marshes, rivers and tarns. Adults have a long season, from February or March until late autumn although they are long-lived, overwintering among grass tussocks or in the soil, and occasionally active during mild winter spells. Host plants include Cruciata laevipes Opiz (smooth bedstraw), and various species of Asperula L. (woodruff) and  Galium L. (Bedstraws) including G. aparine L. (Cleavers), G. mollugo L. (Hedge Bedstraw), G. odoratum (L.) (Sweet scented Bedstraw), G. saxatile L. (Heath Bedstraw), G. uliginosum L. (Fen Bedstraw) and G. verum L. (Lady’s Bedstraw). Adults are diurnal, early in the season they occur low down on the stems or among tussocks but soon ascend the developing plants and feed openly on the foliage, they mate in early summer and oviposition begins in July and continues late into the summer. Early eggs will produce summer larvae and a late generation of adults while those laid later will overwinter and produce larvae in the spring; they are laid individually or in small groups on the host and covered in plant debris and secretions, each female will lay up to 100 eggs which hatch within a few days. Larval development is rapid; they feed on the leaves and stems of the host, passing through 3 instars and becoming fully-grown within six to eight weeks, those developing in the spring will produce adults from May while summer larvae produce adults from August, and when fully-grown they descend the stems and burrow into the soil to pupate and adults eclose after about three weeks. All stages are distinctive; eggs are pale orange or yellow and relatively large, around 2.5mm, while the larvae are metallic greenish or blue with the head and thorax shiny compared with the dull abdomen, they are fat and bloated in appearance with deep folds between the abdominal segments. The pupa is a striking orange-red with a single long apical tubercle. Adults have the wings reduced or missing and the elytra fused and so are incapable of flight.

Large, 8-13mm, and convex with separately rounded pronotum and elytra, entirely dark with a weak blue, violet or coppery reflection, the pronotum and elytra somewhat dull due to the uneven surface, rather strong and dense punctation and fine isodiametric microsculpture (X40). Among the UK fauna it might be mistaken for the generally larger (11-18mm) T. tenebricosa (Fabricius, 1775) but here the pronotum is strongly widened anteriorly and the dorsal surface has strong microsculpture which is obvious at X20, or various species of Chrysolina Motschulsky, 1860, here the elytral epipleura are reflexed under the body, narrowed posteriorly and delimited by a sharply raised line; in Timarcha the epipleura are almost vertical, wide throughout their length and delimited by a broad and ill-defined ridge which is sometimes present as a shallow and wide convexity. Males are distinguished by the much more strongly dilated tarsal segments.

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