Elateridae of the British Isles

Synaptus filiformis (Fabricius, 1781)

Size – 9-13mm.

Description – A noticeably elongated species. Uniformly chestnut brown with a dense covering of lighter brown/cream coloured hairs. The antennae are very long, extending a way beyond the posterior edge of the pronotum.

National Biodiversity Network map showing the distribution of Synaptus filiformis across Britain and Ireland.

British and Irish distribution of Synaptus filiformis (Fabricius, 1781) based on records held by the National Biodiversity Network.

Distribution data supplied by:

  • Countryside Council for Wales
  • Natural England
  • Countryside Council for Wales

Distribution – Only a handful of British records from around the Severn area and North Yorkshire.

Biology - Details of the larval stage of this species appear unclear with some sources stating development is in waterlogged soils, but others suggesting they may inhabit dead wood. Imago insects emerge in May and are present until July or August. They can be found by beating the foliage of various tree species, particularly Willow (Salix spp.), Alder (Alnus glutinosa) and Poplar (Populus spp.). Can also be found resting on Hawthorn (Crataegus monogyna) blossom and a range of herbaceous plants and grass species, particularly Reed Canary-Grass (Phalaris arundinacea).

Habitat – Predominantly river banks, but also fens and wet woodland.