Hornet Robberfly (Asilus crabroniformis)
Key Details
| Taxonomic Groups: | Invertebrate > insect - true fly (Diptera) > Soldier fly or ally |
| Red List Status: | Least Concern (Not Relevant) [LC(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: | Asilus crabroniformis |
| 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: | Distribution has declined over the past 35 years with loss of habitat and low potential for expansion of range being major factors |
| Question 2: | Does recovery/ conservation depend on species-specific actions? |
| Response: | Yes |
| Justification: | According to Stubbs and Drake (2014) the populations can be transient and die out as habitats decline meaning expansion and growth of populations is unlikely due to loss of suitable sites. Targeted management will be required to maintain current populations even if expansion of the range is limited. |
| 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: | Potentially habitat management outside of, but close known sites, may allow some expansion of the range but this is limited by the species own limitations when it comes to dispersal distances (reported are up to 500-600m). Management in these areas for other Orders requiring mixed sward heights and bare ground would benefit if grazing present. |
Species Assessment
| Current step on the Species Recovery Curve (SRC): | 6. Recovery solutions trialled |
| Recovery potential/expectation: | Low - Life history factor/s |
| National Monitoring Resource: | Combination - insufficient |
| Species Comments: | The species requires heath, limestone and chalk downs, grassland (commons) and unimproved neutral pasture with horse, cattle or rabbit grazing - the habitats are only relevant if the correct grazing regime and site management is in place for larval development |
Key Actions
Key Action 1
Proposed Action: Mitigation against continuous use of Avermectins in grazing animals, to prevent poisoning of larva and food sources, within the dung that is required for larval development
Action targets: 4. Autecology and pressures understood
Action type: Advice & support
Duration: >10 years
Scale of Implementation: ≤ 100 sites
High priority sites: Known sites already under management/protection such as SSSI's, National Nature Reserves etc and adjoining areas where the fly is present or could be. See Action 3
Comments: See Action 3
Key Action 2
Proposed Action: Restoration of heath from forestry, arable or improved grassland to promote recovery of supporting habitat of this species
Action targets: 5. Remedial action identified
Action type: Habitat creation
Duration: Unknown
Scale of Implementation: ≤ 100 sites
High priority sites: Known sites adjoining those already under management/protection such as SSSI's, National Nature Reserves etc. See Action 3
Comments: See Action 3
Key Action 3
Proposed Action: National monitoring of sites and surroundings to ascertain/ identify areas where habitat creation can be implemented around protected areas.
Action targets: 3. National Monitoring Plan agreed and implemented
Action type: Targeted monitoring
Duration: 3-5 years
Scale of Implementation: ≤ 500 sites
High priority sites: Known sites adjoining those already under management/protection such as SSSI's, National Nature Reserves etc.
Comments: High priority sites need to be identified through monitoring before habitat management and creation can be implemented. Utilisation of Soldierflies and their Allies recording scheme?
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.