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SPECIES MANAGEMENT SHEET
(Spiriverpa lunulata)
Northern silver-stiletto
The Northern silver-stiletto fly is a rare species
strongly associated with exposed river shingle
and sandy sediment deposits. The adults
have an elongated silvery body with silvery-
white hairs on the abdomen and face. The
larvae are predators of insect larvae in sandy
flood deposits. Adults feed on nectar and
pollen from flowers and can be found basking
in sunny spots on sandy banks. Hovering
swarms of males can occasionally be
encountered. This is a UK Biological Action
Plan priority species, a Red Data Book
species, it is on the Scottish Biodiversity List,
and is a priority species in the Cairngorms
Nature Action Plan.
Life cycle
Adults have been recorded from April through to
September, with a peak from mid to late June.
Swarms of hovering males may form on riverbanks
and females enter the swarm to mate. Adults have
been reared from larvae found in sandy river
sediments and are carnivorous, likely hunting
various insect larvae and earthworms.
Distribution map
This is a northern European species with records from
the north and west of Britain, Norway, Sweden and
Finland. The majority of the British population is found
in the Central Scottish Highlands around the Spey
Valley and Easter Ross, but there
are records from the Scottish
Borders, Dumfries & Galloway,
Perthshire, Stirlingshire and
some western counties of
England and Wales.
Habitat
This species is associated with
open areas of exposed sediment
along sandy or stony rivers,
upland streams and around
sandy floodplain deposits. Sandy
river banks with sparse vegetation that are unshaded by
trees and receive regular deposits of loose sediment from
floods or spate events are favoured by adults. The exact
requirements of the larvae are poorly known, but they
appear to need an abundance of exposed sandy deposits.
Dark green post-1980, light green pre-1980
Left: Northern silver-stiletto fly (Spiriverpa lunulata) Right: Exposed riverine shingle next to River Tay at Kercock (typical habitat)
Reasons for decline
This species may be threatened by river
‘improvement’ and flood prevention schemes that
alter sediment deposition, sand and gravel
extraction, afforestation, excessive trampling and
agricultural pollution.
Habitat management
Measures to help conserve the Northern silver-
stiletto fly (that will also benefit a range of other
rare species) include:
Prevent the removal of gravel and sandy deposits
and maintain exposed areas of sand and shingle
banks in an undisturbed state.
Avoid changes to river management that would
prevent regular deposition and movement of
sediment by spate and flood events.
Prevent the encroachment of trees and scrub
close to river banks that would shade exposed
areas of sand used for breeding.
Avoid the build-up of herbaceous vegetation on
exposed riverine sediments that will cover
breeding habitat.
Avoid the use of agricultural chemicals and
pesticides near watercourses.
References:
This sheet can be accessed on the web at www.buglife.org.uk
Stubbs, A.E. and Drake, M. (2001) British Soldierflies and their Allies, BENHS.
Oldroyd, H. (1969) Diptera, Brachycera, Section (a) – Tabanoidea and Asiloidea. Handbooks for the Identification of British Insects, 9 (4): 1-132
Drake, C. M. , Godfrey, A.G., Hewitt, S. and Parker, J. (2007) Fly assemblages of Exposed Riverine Sediment.– final Report. Buglife publication.
Buglife—The Invertebrate Conservation Trust, Balallan House, 24 Allan Park, Stirling, FK8 2QG
Buglife—The Invertebrate Conservation Trust is a company limited by guarantee.
Registered in England at Bug House, Ham Lane, Orton Waterville, Peterborough, PE2 5UU. Company no. 4132695,
Registered charity no, 1092293, Scottish charity no. SC040004
Photographs of Spiriverpa lunulata © Roger Key; Habitat photographs © Steve Hewitt
Acknowledgements: Steve Hewitt and Martin Drake, Diptera experts
www.buglife.org.uk Tel: 01786 447 504 @buzz_dont_tweet
Survey methodology
Surveying should ideally take place between May—
late July, roughly between 10am—4pm during dry and
sunny weather conditions.
Sweep netting river bank areas deemed suitable to
support the adult fly should be carried out. Searching
on the bare sand banks should also be checked for
resting adults.
Care is needed to ensure that a similar stiletto fly
Acrosathe annulata, also found in the Spey Valley, is
discounted (this specimen is almost identical to
Spiriverpa lunulata in the field). Voucher specimens
will need to be collected and identified to confirm the
presence of the Northern silver stiletto fly.
A sufficiently experienced surveyor should be
employed to conduct the survey.
Left: Exposed riverine shingle habitat next to River Feshie Speyside; Right: Northern sllver-stiletto (Spiriverpa lunulata)
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