Bog Hoverfly (Eristalis cryptarum)
Key Details
| Taxonomic Groups: | Invertebrate > insect - true fly (Diptera) > Hoverfly |
| Red List Status: | Critically Endangered (Not Relevant) [CR(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: | Eristalis cryptarum |
| UKSI Recommended Authority: | (Fabricius, 1794) |
| UKSI Recommended Qualifier: | (none specified) |
| Red List Citation: | Ball & Morris, 2014 |
| Notes on taxonomy/listing: | (none) |
Criteria
| Question 1: | Does species need conservation or recovery in England? |
| Response: | Yes |
| Justification: | Incredibly rare, with modern records confined to a few sites in South Dartmoor. Seemingly lost from Dorset. The New Forest and Cornwall. Unknown elsewhere in UK. |
| Question 2: | Does recovery/ conservation depend on species-specific actions? |
| Response: | Yes |
| Justification: | It is felt that protection of unpolluted M29 soakaways within valley mire (usually indicated by abundant Marsh St John's-wort and Bogbean) could be important for larval development . This means getting grazing levels right to prevent scrub encroachment. It seems to be a poor competitor against other Eristalis species and does best where flowers of umbellifers and composites (which attract other Eristalis) are scarce or absent, and no eutrophication is taking place. |
| 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: | Yes |
| Justification: | It clearly requires clusters of intact and unpolluted valley mire systems with a variety of microhabitats, including M29 soakaways and good patches of Bogbean and heathers for adult feeding. |
Species Assessment
| Current step on the Species Recovery Curve (SRC): | 4. Autecology and pressures understood |
| Recovery potential/expectation: | Low - Combination or other (detail in comments) |
| National Monitoring Resource: | Opportunistic - insufficient |
| Species Comments: | Formal surveying is sporadic. Some amateur recording takes place but mostly at known sites, ignoring other potential sites. |
Key Actions
Key Action 1
Proposed Action: Map/monitor the valley mires with M29 soakaway-rich mires in Dartmoor.
Action targets: 4. Autecology and pressures understood
Action type: Scientific research
Duration: 3-5 years
Scale of Implementation: ≤ 20 sites
High priority sites: Valley mires of Dartmoor including those of Buckland Moor, the Challacombe area and Pizwell area.
Comments: Eristalis cryptarum seems to require fairly specific mire conditions.
Key Action 2
Proposed Action: Specific targeted surveying/monitoring in the key areas identified by Action 1 to investigate the extent of populations and current status (to feed into a revision of the Red List)and whether there are specific habitat needs.
Action targets: 4. Autecology and pressures understood
Action type: Scientific research
Duration: 2 years
Scale of Implementation: ≤ 20 sites
High priority sites: Dartmoor mires plus worth checking some suitable sites in the New Forest and Dorset heaths to see if it has survived here.
Comments:
Key Action 3
Proposed Action: At occupied sites, research is required to analyse site-specific habitat resource, land management and pressures to aid recovery of this species
Action targets: 4. Autecology and pressures understood
Action type: Scientific research
Duration: 1 year
Scale of Implementation: ≤ 20 sites
High priority sites: All occupied sites
Comments: Mainly desk-sourced information that complements Actions 1 and 2, to be carried out within the same contract.
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.