Hydrochus megaphallus
Key Details
| Taxonomic Groups: | Invertebrate > insect - beetle (Coleoptera) > Water beetle |
| Red List Status: | Vulnerable (Not Relevant) [VU(nr)] |
| D5 Status: | Included in the baseline Red List Index for England (Wilkins, Wilson & Brown, 2022) |
| Section 41 Status: | (not listed) |
| Taxa Included Synonym: | (none) |
| UKSI Recommended Name: | Hydrochus megaphallus |
| UKSI Recommended Authority: | van Berge Henegouwen, 1988 |
| 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: | Hydrochus megaphallus was recognised as new to science in 1988. It appears to be restricted to river-valley fens in the Broads and Redgrave & Lopham Fen on the Suffolk/Norfolk border. While examination of museum material has revealed a specimen from Leicestershire collected in the 1900s, there is no other indication that H. megaphallus was more widespread in the past. It might therefore be considered a 'natural rarity' but its extremely localised distribution in Britain (5 hectads, all in East Anglia) makes it vulnerable to extinction. Broadland sites may be at risk from sea level rise in the medium to long term. |
| Question 2: | Does recovery/ conservation depend on species-specific actions? |
| Response: | Yes |
| Justification: | Action is needed to improve and promote better understanding of the species' conservation requirements, including on protected sites. This could be done through an assemblage approach (see Species Comments). |
| 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: | As a very rare, sedentary habitat specialist, H. megaphallus is unlikely to benefit from untargeted habitat management. |
Species Assessment
| Current step on the Species Recovery Curve (SRC): | 4. Autecology and pressures understood |
| Recovery potential/expectation: | Unknown |
| National Monitoring Resource: | Opportunistic - insufficient |
| Species Comments: | Hydrochus megaphallus belongs to a suite of water beetles apparently dependent on relict fens. Others include Agabus striolatus, Dryops anglicanus, D. auriculatus, D. griseus, Helochares obscurus, Hydraena palustris, Hydrochus brevis, H. ignicollis, Hydroporus elongatulus, H. glabriusculus, H. scalesianus, Laccornis oblongus & Limnebius aluta (Agabus labiatus and A. undulatus may also be relevant). These insects occur mostly on protected sites but their needs may not be recognised or given due priority in, for example, designation documents, water level management plans and habitat management plans. It is recommended that a 'grouped action plan' approach is taken for these species. This should aim for a definitive inventory and categorisation of such species, identify conservation management requirements and ensure that relevant species are considered in management plans for protected sites where they occur. 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: Make an inventory of all protected sites with post-1980 records. Consider opportunities for listing this species as a site 'feature' (e.g. review of SSSI citations).
Action targets: 5. Remedial action identified
Action type: Site protection
Duration: 2 years
Scale of Implementation: National
High priority sites: Records have been mapped in Atlas 2 (Foster et al, 2018).
Comments: Relevant to all sites in inventory.
Key Action 2
Proposed Action: Undertake a review of this species and other water beetles dependent on relict-fens in order to promote better understanding of their conservation requirements. Hydrochus megaphallus belongs to a suite of water beetles closely associated with remnant fens; others include Agabus striolatus, Dryops anglicanus, D. auriculatus, D. griseus, Helochares obscurus, Hydrochus brevis, H. ignicollis, Hydroporus elongatulus, H. glabriusculus, H. scalesianus, Laccornis oblongus and Limnebius aluta.
Action targets: 4. Autecology and pressures understood
Action type: Scientific research
Duration: 1 year
Scale of Implementation: National
High priority sites:
Comments:
Key Action 3
Proposed Action: Advise site managers on the presence and requirements of this species in consideration of SSSI, nature reserve management, and other land management, especially pond restoration and water level control.
Action targets: 5. Remedial action identified
Action type: Advice & support
Duration: 2 years
Scale of Implementation: National
High priority sites:
Comments:
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.