Diving beetle (Lancetes)

Taxonomic group

Dytiscidae: Lancetes

Diagnostic features

Lancetes is one of the dytiscid “diving beetles” having larvae (which we haven’t managed to photograph yet) resembling those of Rhantus, lacking any nose-like projection. The larvae have 2 tail-like cerci that are twice the length of the last abdominal segment (Rhantus cerci are about as long as the last segment). The adults are oval and streamlined, 8 to 12mm long, with 11-segmented antennae, and are distinguished by strong yellow and black stripes.

[Lancetes] adult with strong yellow and black striping. Image: Stephen Moore Image — Lancetes adult with strong yellow and black striping. Image: Stephen Moore

Typical habitats

Lancetes are most likely to be found in weedy ponds, and slow-flowing streams.

Feeding

The dytiscid beetles are predators, feeding on other pond invertebrates.

Indicator value

Hard bottom: unassigned; general dytiscids value 5
Soft bottom: unassigned; general dytiscids value 0.4

The tolerance values (ranging from 0 to 10) give an indication of which are the sensitive taxa (values of 8 or more) and which are the tolerant taxa (values of 3 or less). For more information see: Indicator species

The presence of Lancetes is more likely to reflect pond-like habitat conditions rather than any particular water quality conditions. This genus has not been assigned tolerance values but the dytiscids have family scores of 5 (hard bottom sites) and 0.4 (soft bottom sites).