Diving beetle (Agabus brunneus)

KingdomAnimalia
PhylumArthropoda
ClassInsecta
OrderColeoptera
FamilyDytiscidae
GenusAgabus
SizeLength: 9-9.5 mm

Classified as Vulnerable in the UK.

This chocolate-brown beetle has no common English name. It is difficult to distinguish from a number of similar species, needing the close scrutiny of a feature on the underside of the beetle called the prosternal process. This is a small, spear-shaped projection just behind the head of the beetle between the first pair of legs.

This beetle's range in centred on the Mediterranean, with its northern-most outposts in Belgium and southern Britain. It occurs in only two parts of the UK, west Cornwall and around the New Forest in Hampshire, although a recent survey found a specimen in Dorset.

This species prefers shallow, swift-flowing, open lowland streams with a gravel or flint bed

It is thought that this beetle lives in the gravel beds of streams and lays its eggs in autumn. Larvae have been collected in January and March so it appears that the beetle over-winters in this stage in the UK. However, it is also believed that the beetles may breed in the spring in the warmer southern coastal sites. This species is unable to fly.

Agabus brunneus is vulnerable to a number of factors that can affect its habitat. Water abstraction, changes in drainage systems and pollution are all potential hazards. It is also susceptible to the shading of streams by ungrazed vegetation.

This diving beetle is listed as a priority species by the UK Biodiversity Action Plan (UKBAP), and is included in English Nature's Species Recovery Programme.It is proposed that viable populations are maintained at a total of five sites by 2010, and that considerations for management of the beetle habitat should influence agri-environment schemes and drainage projects within the areas where the beetle occurs. Other water-living species will benefit from the same management regimes, one of them being the freshwater crayfish (Austropotamobius pallipes). This is a frequent occurrence when drawing up management plans for species that share a similar habitat, and it illustrates how work on one species can improve our knowledge of another that may also require conserving.

Information supplied by English Nature.

http://www.english-nature.org.uk