Microdon devius
Key Details
| Taxonomic Groups: | Invertebrate > insect - true fly (Diptera) > Hoverfly |
| Red List Status: | Near Threatened (Not Relevant) [NT(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: | Microdon devius |
| UKSI Recommended Authority: | (Linnaeus, 1761) |
| 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: | In England, records are concentrated within a relatively small number of sites within the North Downs, western South Downs, Chilterns and East Anglian Brecks. Some of these sites are vulnerable to succession or changes in grazing management. Also known from some sites in North Wales. Near Threatened in Europe (IUCN). |
| Question 2: | Does recovery/ conservation depend on species-specific actions? |
| Response: | Yes |
| Justification: | This species has multiple habitats associations in England. Most populations are associated with Lasius flavus nests on short-cropped chalk grassland (especially south-facing downland scarps). Some East Anglian populations seem to be associated with the same ant but in flat Breck chalk-heath locations (e.g. Thompson and Foulden Commons). A few other populations occur in fens, possibly using a different host ant. At its downland and Breckland sites, specific measures to protect and promote short-cropped grassland with plentiful ant hills are vital for the conservation of this species, which is vulnerable to succession on the one hand but also excessive disturbance (by overgrazing or trampling) on the other. Species-specific action requirements at its fenland sites are less obvious. |
| 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: | Relatively sedentary grassland insects such as this clearly benefit from landscape scale management of high quality chalk grassland featuring a range of grassland conditions. Those conditions must protect and promote ant hill-rich areas. |
Species Assessment
| Current step on the Species Recovery Curve (SRC): | 5. Remedial action identified |
| Recovery potential/expectation: | Low - Relict or natural rarity |
| National Monitoring Resource: | Opportunistic - insufficient |
| Species Comments: | Most data is from sporadic amateur surveying, little of which is structured. |
Key Actions
Key Action 1
Proposed Action: Map areas of chalk grassland with plentiful ant hills in and around the known hotspots to identify the best management regimes for sustaining and promoting and hills.
Action targets: 4. Autecology and pressures understood
Action type: Scientific research
Duration: 3-5 years
Scale of Implementation: ≤ 50 sites
High priority sites: North Downs, Chilterns, west end of South Downs, Breckland.
Comments: Promoting the abundance of Lasius flavus ant hills in short-cropped grassland seems to be the key to conserving this hoverfly.
Key Action 2
Proposed Action: Specific targeted surveying/monitoring in the key area identified by Action 1 to investigate the extent of populations and whether there are specific habitat needs.
Action targets: 4. Autecology and pressures understood
Action type: Scientific research
Duration: 2 years
Scale of Implementation: ≤ 50 sites
High priority sites: North Downs, Chilterns, Norfolk Commons
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.