Diving beetle (Bidessus minutissimus)

SizeLength: 1.5 mm (1)

Classified as Rare in Great Britain (2).

This very small diving beetle is patterned with black and yellow blotches (3). It is beautifully adapted for life in water, with a sleek, streamlined body and modified hair-fringed hind legs, which are used as paddles (4).

This beetle is found only in western parts of Britain, and was once found from the Solway area as far south as Devon. Since 1908 there have been no records of this species in southern England, but it was found in 1981 in Cheshire (2). It has recently been recorded from four rivers in Wales, and there are historic records from two others. In Scotland it is currently known from only one of five rivers it has been recorded from in the past (5). Elsewhere, this beetle is found in southern Ireland, the Canaries, North Africa, central Europe, Switzerland, Austria, Italy and the Balearics (2).

Found in the lower parts of rivers (although not in brackish water), where it is often associated with fine gravel or sand banks. Previously it has been found in coastal lakes (2).

The details of the life cycle of this water beetle are unknown, and larval stages have not been observed. It is able to fly (2).

This species is currently threatened by water pollution, disturbance by anglers and boat users, as well as changes to the riverbanks, such as strengthening (2).

This beetle is a priority species under the UK Biodiversity Action Plan (UK BAP), and a Species Action Plan has been produced to guide its conservation; the Environment Agency is the 'lead partner' responsible for coordinating efforts to conserve this species (1).

Information authenticated by Adrian Fowles of the Countryside Council for Wales:

  1. Environment Agency (2000) Focus on Biodiversity. Environment Agency, Bristol.
  2. UK BAP (September 2002): http://www.ukbap.org.uk
  3. National Biodiversity Network Species Dictionary (March 2003): http://www.nhm.ac.uk/nbn/
  4. Harde, K. W. (2000) A field guide in colour to beetles. Silverdale Books, Leicester.
  5. Fowles, A. (2003) Pers. comm.