Crucifix ground beetle (Panagaeus crux-major)

SizeBody length: 8 - 10 mm

Classified as Vulnerable in the UK.

This rare beetle is largely black and very bristly. In shape, it has a characteristic bug-eyed appearance and a broad thorax. The English name was inspired by the large red spots on the wing cases which extend over the margins, giving the appearance of a black cross against a red background.

Only known today from four sites: the Lower Derwent Valley in Yorkshire, Pembrey Burrows in Dyfed, Wales, Saltfleetby and Theddlethorpe Dunes National Nature Reserve in Lincolnshire, and the Rother Valley in Sussex. The beetle was once more widespread in its distribution, being recorded over much of eastern England and parts of the midlands.

The beetle appears to prefer habitats that are periodically inundated, such as floodplains and dune slacks. Many populations in Eire and on mainland Europe are associated with tall sedge fens that, either through grazing or inundation, are open in character above a bare muddy substrate. However, the specimens found in Sussex were on part of a river meander within the valley floodplain.

There is very little known about the life of the crucifix ground beetle. It is nocturnal in its activities, like most ground beetles, and from searches carried out it seems to like sheltering under pieces of driftwood or discarded plastic sheets during the day. This beetle is a predatory species, that probably feeds mainly on semi-aquatic snails, but its principal prey isn't known for certain.

It is thought that the main reason for the crucifix ground beetle's disappearance is changes in river and water management over time. The Welsh site has recently been lost due to natural incursions by the sea but other potential habitat survives in the vicinity and the beetle may still be present locally.

The Crucifix ground beetle is listed in the UK Biodiversity Action Plans (UKBAPs), and included in English Nature's Species Recovery Programme (SRP). The Countryside Council for Wales and English Nature are joint ‘lead partners’ responsible for coordinating efforts to conserve this species. There has been a long-running project to search for this species and, so far five individuals have been found at the Lincolnshire site. The small population in Sussex was discovered following examination of flood detritus along the river Rother. The species was last seen in Wales in 1998. There is currently a large project running to examine all the species of ground beetle in Britain and prioritise the rarest 30 species. Once this has reported we shall have a clearer view of the status of more of these intriguing and, in some cases, little known beetles.

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Information supplied by English Nature and the Countryside Council for Wales.