Friday, August 12, 2011

How to Click Like a Beetle

A click beetle, Athous haemorrhoidalis
One of the most common of the 25 species of click beetles (Elateridae) (1), Athous haemorrhoidalis is easily identifiable from its relatively narrow body, reddish-brown eltyra, darker head and thorax and the hairs coating its body that give it a downy appearance (2). The larvae, known as wireworms, feed on the roots of grasses and other plants and they, along with some Agriotes spp. are considered serious agricultural pests of cereal crops and potatoes (3).
A click beetle, Athous haemorrhoidalis
One of the most surprising features of A. haemorrhoidalis (and for the Elateridae as a whole) for someone encountering the beetle for the first time is its tendency to jump into the air, making a loud 'click' in the process, when alarmed. This action is achieved by the rapid sliding of a peg or spine located on the underside of the prosternum down a smooth track on the mesosternum (4). The beetle is propelled vertically up to 0.3 m high, turning head over tail several times during a jump. While an impressive (and entertaining) sight, this actual jumping action has been shown to be quite inefficient, with only 50-60% of energy expended in a jump is energy of translation, which actually raises the beetle (5).

  1. Ferriss et al., 2009. Irish Biodiversity: a Taxonomic Inventory of Fauna p. 98
  2. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 148
  3. Gibbons, 1999. Insects of Britain and Europe p. 207
  4. Evans, 1972. Journal of Zoology 167 pp. 319-336
  5. Evans, 1973. Journal of Zoology 169 pp. 181-194

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