Silky Wave (Idaea dilutaria)
Key Details
| Taxonomic Groups: | Invertebrate > insect - moth > Moth |
| Red List Status: | (Not Relevant) [(not listed)(nr)] |
| D5 Status: | |
| Section 41 Status: | (not listed) |
| Taxa Included Synonym: | (none) |
| UKSI Recommended Name: | Idaea dilutaria |
| UKSI Recommended Authority: | (Hübner, [1799]) |
| UKSI Recommended Qualifier: | (none specified) |
| Red List Citation: | (not listed) |
| Notes on taxonomy/listing: | (none) |
Criteria
| Question 1: | Does species need conservation or recovery in England? |
| Response: | Yes |
| Justification: | GB Red List (Fox et al. 2019): NT. Only 3 isolated GB populations, one of which is in England (Avon Gorge). Bespoke monitoring indicates this population is increasing, but it remains vulnerable due to the need for ongoing habitat management. |
| Question 2: | Does recovery/ conservation depend on species-specific actions? |
| Response: | Yes |
| Justification: | Breeds in limestone grassland with scattered scrub, which requires ongoing management to ensure a suitable mosaic of grassland and scrub areas is maintained. |
| 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: | Needs grassland/scrub mosaics on limestone, but too restricted in distribution to benefit from wider landscape measures. |
Species Assessment
| Current step on the Species Recovery Curve (SRC): | 7. Best approach adopted at appropriate scales |
| Recovery potential/expectation: | Medium-high |
| National Monitoring Resource: | Structured - sufficient |
| Species Comments: | Additional habitat in the Avon Gorge landscape could be brought into suitable condition for the moth, which would increase the resilience of this isolated population. |
Key Actions
Key Action 1
Proposed Action: Silky Wave requires periodic scrub clearance to maintain sites in good condition for the moth. Ensure known subsites in the Avon Gorge are managed appropriately, through rotational scrub clearance and/or grazing.
Action targets: 7. Best approach adopted at appropriate scales
Action type: Habitat management
Duration: 6-10 years
Scale of Implementation: 1 site
High priority sites: Avon Gorge
Comments: Scrub clearance on 6-10 year rotation depending on speed of scrub development
Key Action 2
Proposed Action: Clear secondary woodland from additional areas of the Avon Gorge; monitor development of limestone grassland habitat and colonisation by Silky Wave.
Action targets: 6. Recovery solutions trialled
Action type: Habitat management
Duration: 3-5 years
Scale of Implementation: 1 site
High priority sites: Avon Gorge
Comments:
Key Action 3
Proposed Action: The main larval host plant is thought to be Common Rock-rose (Helianthemum nummularium). However, subsites on the south side of the Avon Gorge have little or no Helianthemum present and the moth is likely to be using alternative host plant(s). Conduct larval surveys to determine the host plants used at these subsites.
Action targets: 4. Autecology and pressures understood
Action type: Scientific research
Duration: 2 years
Scale of Implementation: 1 site
High priority sites: Avon Gorge
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.