Northern Silver-Stiletto (Spiriverpa Lunulata)

SPECIES MANAGEMENT SHEET Northern silver-stiletto (Spiriverpa lunulata)

Left: Northern silver-stiletto fly (Spiriverpa lunulata) Right: Exposed riverine shingle next to River Tay at Kercock (typical habitat)

The Northern silver-stiletto fly is a rare species Distribution map strongly associated with exposed river shingle This is a northern European species with records from and sandy sediment deposits. The adults the north and west of Britain, Norway, Sweden and have an elongated silvery body with silvery- Finland. The majority of the British population is found white hairs on the abdomen and face. The in the Central Scottish Highlands around the Spey larvae are predators of insect larvae in sandy Valley and Easter Ross, but there flood deposits. Adults feed on nectar and are records from the Scottish pollen from flowers and can be found basking Borders, Dumfries & Galloway, in sunny spots on sandy banks. Hovering Perthshire, Stirlingshire and swarms of males can occasionally be some western counties of England and Wales. encountered. This is a UK Biological Action Plan priority species, a Red Data Book Habitat species, it is on the Scottish Biodiversity List, and is a priority species in the Cairngorms This species is associated with Nature Action Plan. open areas of exposed sediment along sandy or stony rivers, Dark green post-1980, light green pre-1980 Life cycle upland streams and around sandy floodplain deposits. Sandy Adults have been recorded from April through to river banks with sparse vegetation that are unshaded by September, with a peak from mid to late June. trees and receive regular deposits of loose sediment from Swarms of hovering males may form on riverbanks floods or spate events are favoured by adults. The exact and females enter the swarm to mate. Adults have requirements of the larvae are poorly known, but they been reared from larvae found in sandy river appear to need an abundance of exposed sandy deposits. sediments and are carnivorous, likely hunting various insect larvae and earthworms. Left: Exposed riverine shingle habitat next to River Feshie Speyside; Right: Northern sllver-stiletto (Spiriverpa lunulata)

Reasons for decline Survey methodology

This species may be threatened by river  Surveying should ideally take place between May— ‘improvement’ and flood prevention schemes that late July, roughly between 10am—4pm during dry and alter sediment deposition, sand and gravel sunny weather conditions. extraction, afforestation, excessive trampling and  Sweep netting river bank areas deemed suitable to agricultural pollution. support the adult fly should be carried out. Searching

on the bare sand banks should also be checked for Habitat management resting adults. Measures to help conserve the Northern silver-  Care is needed to ensure that a similar stiletto fly stiletto fly (that will also benefit a range of other Acrosathe annulata, also found in the Spey Valley, is rare species) include: discounted (this specimen is almost identical to  Prevent the removal of gravel and sandy deposits Spiriverpa lunulata in the field). Voucher specimens and maintain exposed areas of sand and shingle will need to be collected and identified to confirm the banks in an undisturbed state. presence of the Northern silver stiletto fly.

 Avoid changes to river management that would  A sufficiently experienced surveyor should be prevent regular deposition and movement of employed to conduct the survey. sediment by spate and flood events. References:  Prevent the encroachment of trees and scrub close to river banks that would shade exposed This sheet can be accessed on the web at www.buglife.org.uk areas of sand used for breeding. Stubbs, A.E. and Drake, M. (2001) British Soldierflies and their Allies, BENHS.  Avoid the build-up of herbaceous vegetation on Oldroyd, H. (1969) Diptera, Brachycera, Section (a) – exposed riverine sediments that will cover Tabanoidea and Asiloidea. Handbooks for the Identification of breeding habitat. British Insects, 9 (4): 1-132

 Avoid the use of agricultural chemicals and Drake, C. M. , Godfrey, A.G., Hewitt, S. and Parker, J. (2007) Fly assemblages of Exposed Riverine Sediment.– final Report. pesticides near watercourses. Buglife publication.

www.buglife.org.uk Tel: 01786 447 504 @buzz_dont_tweet Buglife—The Invertebrate Conservation Trust, Balallan House, 24 Allan Park, Stirling, FK8 2QG

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Acknowledgements: Steve Hewitt and Martin Drake, Diptera experts