Diving Beetle (Hydroporus necopinatus)
Key Details
| Taxonomic Groups: | Invertebrate > insect - beetle (Coleoptera) > Water beetle |
| Red List Status: | Endangered (Not Relevant) [EN(nr)] |
| D5 Status: | Included in the baseline Red List Index for England (Wilkins, Wilson & Brown, 2022) |
| Section 41 Status: | (not listed) |
| Taxa Included Synonym: | Hydroporus necopinatus subsp. roni, Ron's Diving Beetle |
| UKSI Recommended Name: | Hydroporus necopinatus |
| UKSI Recommended Authority: | Fery, 1999 |
| UKSI Recommended Qualifier: | (none specified) |
| Red List Citation: | Foster, 2010 |
| Notes on taxonomy/listing: | (none) |
Criteria
| Question 1: | Does species need conservation or recovery in England? |
| Response: | Yes |
| Justification: | In England, 'H. necopinatus' is recorded from only 4 hectads in and around the Isle of Purbeck, Dorset (Foster et al 2016). However, populations of the closely-related Hydroporus melanarius in the New Forest and on The Lizard appear to have undergone hybridisation with this taxon in the past. Note that Hydroporus necopinatus ssp. roni is the name given to the Dorset population and would not apply to the hybrid New Forest/Lizard populations; this taxon is listed as a NERC Act S41 'species of principal importance'. |
| Question 2: | Does recovery/ conservation depend on species-specific actions? |
| Response: | Yes |
| Justification: | H. necopinatus is naturally rare but as subspecies roni is confined globally to England, it must merit conservation action. Restricted to Purbeck (Dorset) area. Taxonomic research needed. |
| Question 3: | At a landscape scale, would the species benefit from untargeted habitat management to increase habitat mosaics, structural diversity, or particular successional stages? |
| Response: | No |
| Justification: | This taxon is too localised to benefit from wider countryside measures. |
Species Assessment
| Current step on the Species Recovery Curve (SRC): | 5. Remedial action identified |
| Recovery potential/expectation: | Unknown |
| National Monitoring Resource: | Opportunistic - insufficient |
| Species Comments: | Hydroporus necopinatus subsp. roni is S41 listed but is treated under species rank here. Ad hoc recording as part of GB water beetle recording scheme (Balfour-Browne Club/Aquatic Coleoptera Conservation Trust) |
Key Actions
Key Action 1
Proposed Action: Develop a 5 year action plan for Hydroporus necopinatus (subsp. roni) in consultation with local experts and stakeholders. This should identify ways of maintaining and increasing the core Isle of Purbeck population. It should anticipate effects of climate change such as the likelihood of existing pool systems drying-out earlier.
Action targets: 5. Remedial action identified
Action type: Education/awareness raising
Duration: 1 year
Scale of Implementation: Unknown
High priority sites: Isle of Purbeck and western edge of New Forest (Foster et al, 2016)
Comments: Relevant to 4 occupied hectads. Hydroporus necopinatus roni exploits a range of small pools, ditches and runnels on heathland including those created by military activities. Identifying opportunities to expand and increase the resilience of habitats for this taxon will require close consultation with partners with detailed local knowledge.
Key Action 2
Proposed Action: Undertake (further) genetic studies to elucidate the relationship between H. necopinatus roni and populations of Hydroporus melanarius in the New Forest and on the Lizard.
Action targets: 1. Taxonomy established
Action type: Scientific research
Duration: 2 years
Scale of Implementation: ≤ 5 sites
High priority sites: Isle of Purbeck sites/New Forest/The Lizard
Comments: As H. necopinatus roni appears to be a genuine English endemic, it is important to delineate taxon boundaries and understand better its relationship with H. melanarius.
Acknowledgment:
Data used on this website are adapted from Threatened species recovery actions 2025 baseline (JP065): Technical report and spreadsheet user guide (Natural England, 2025). Available here.