Water scavenger beetle (Limnoxenus)

Taxonomic group

Hydrophilidae: Limnoxenus

Diagnostic features

Limnoxenus is a large hydrophilid beetle with adults 9mm in length (much larger than most NZ freshwater species). The underside of the thorax is keel-shaped. The adults have long swimming hairs on the tarsi (last leg segments). They have a 5-segmented abdomen and 9-segmented antennae. We don’t have a description of the larvae.

[Limnoxenus] adult with long swimming hairs. Image: Stephen Moore Image — Limnoxenus adult with long swimming hairs. Image: Stephen Moore

[Limnoxenus] adult. Image: Stephen Moore Image — Limnoxenus adult. Image: Stephen Moore

Typical habitats

Limnoxenus are rarely found, but they are known from weedy ponds.

Feeding

The larvae are likely to be predators, but as in other hydrophilids the adults may also scavenge on streambed detritus.

Indicator value

Hard bottom: unassigned; general hydrophilid value 5
Soft bottom: unassigned; general hydrophilid value 8.0

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 Limnoxenus 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 hydrophilids have family scores of 5 (hard bottom sites) and 8.0 (soft bottom sites).