Barred Green Colonel (Odontomyia hydroleon)
Key Details
| Taxonomic Groups: | Invertebrate > insect - true fly (Diptera) > Soldier fly or ally |
| 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: | Odontomyia hydroleon |
| UKSI Recommended Authority: | (Linnaeus, 1758) |
| UKSI Recommended Qualifier: | (none specified) |
| Red List Citation: | Drake, 2017 |
| Notes on taxonomy/listing: | (none) |
Criteria
| Question 1: | Does species need conservation or recovery in England? |
| Response: | Yes |
| Justification: | Originally known from two sites, one of these Banc-y-mwldan, Ceredigion (VC46) has not had any records since 2006, the other, Sieve Dale Fen, North Yorkshire (VC62), is monitored annually and records exist for virtually every year since 1992. Both sites are small and occupied areas around open flushes are even smaller (10's m2) |
| Question 2: | Does recovery/ conservation depend on species-specific actions? |
| Response: | Yes |
| Justification: | Active work to maintain the fen quality at Seive Dale Fen through Forest England Recovery trust. The fly appears to be extinct from Banc-y-mwldan; surveys in 2014-2016 failed to find any specimens. On-site work to maintain habitat and increase areas of occupancy is needed at Seive Dale fen. |
| 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: | Opening up of the landscape between the known site at Seive Dale and nearby sites with similar habitat niches may allow unrestricted access for adults that would normally avoid scrub and overgrown areas. There are two potential areas of interest within 5km of Seive Dale fen; Ellers Woodand Sand Dale SSSI unit 2 and Troutsdale and Rosekirk Dale fens SSSI, both M13 habitats as is Seive Dale fen. |
Species Assessment
| Current step on the Species Recovery Curve (SRC): | 5. Remedial action identified |
| Recovery potential/expectation: | Low - Life history factor/s |
| National Monitoring Resource: | Combination - sufficient |
| Species Comments: | The previous National Monitoring resource applies to Seive Dale Fen. The requirement is for base-rich spring fed sites with fen vegetation and open seepages. The larvae feed on the mud or peat surface and need open short or tussocky vegetation that doesn't shade these areas. |
Key Actions
Key Action 1
Proposed Action: At Seive Dale Fen there is a need to remove willow scrub that threatens the underlying calcareous seepages on which the larvae depend through shading caused by encroachment and potentially could effect water levels.
Action targets: 5. Remedial action identified
Action type: Habitat management
Duration: >10 years
Scale of Implementation: 1 site
High priority sites: Sieve Dale Fen, North Yorkshire (VC62)
Comments: The areas of occupancy within the fen are tiny and protecting these is critical. Removing willow scrub and thus shading is necessary as the larval requirement for unicellular algae is dependant on sunlight.
Key Action 2
Proposed Action: Creation and enhancement of viable habitat for the species through scrub clearance or potentially through sedge and reed cutting to enhance the viability of seepages as suitable habitat
Action targets: 5. Remedial action identified
Action type: Habitat management
Duration: >10 years
Scale of Implementation: 1 site
High priority sites: Sieve Dale Fen, North Yorkshire (VC62)
Comments: To prevent encroachment of reed and any other scrub that may infringe on existing sites, further limiting the area that the species can survive in.
Key Action 3
Proposed Action: Targeted surveys at nearby sites with similar habitats (M13) to see if the fly has further populations in the area. If not then scope out a larval translocation scheme to one of the nearby suitable sites to minimise the risk of stochastic extinction at Seive Dale.
Action targets: 3. National Monitoring Plan agreed and implemented
Action type: Targeted monitoring
Duration: 3-5 years
Scale of Implementation: ≤ 5 sites
High priority sites: Ellers Woodand Sand Dale SSSI unit 2 and Troutsdale and Rosekirk Dale fens SSSI
Comments: The larvae of O. hydroleon can take several years to develop before the adult fly emerges, so targeted regular surveys throughout the adult flight season would be needed over several years. Peak emergence is from the end of June (25th) to mid-July, it is thought that adults only live for a few days so dedicated recording throughout this period would be needed so as not to miss emergence. See NE report Webb, J.A. (2023)
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.