Insects - True Flies

Image above by Rob Wolton
Zipperback hoverfly Chrysotoxum elegans - This attractive species is a striking wasp mimic. A scarce species with a strong association with Devon, its national range and populations are thought to be declining. The larvae have not been found but are likely to associated with ants. This species favours sunny south-facing coastal slopes, often in clearing among gorse and blackthorn scrub. It is threatened by loss of unimproved grassland, especially through scrub invasion reflecting a lack of grazing.

A fly Coenosia pudorosa - This small fly belongs to the house fly family. Classified as Near Threatened with very few recent records nationally, it is strongly associated with wet woodlands, especially in river valleys. Little is known about its biology, but its larvae are probably predators of other fly larvae. It is vulnerable to the clearance of willow scrub and the drainage of wet woodland.

Image above by Rob Wolton
A cranefly Dicranomyia goritiensis - This scarce fly of south-western coasts breeds on steep moss and algal-covered rock faces with water constantly flushing over the surface. It is only known from two inland sites in the UK, one of these being on Dartmoor at Meldon Aplite Quarry. It is threatened by coastal development, changes in water chemistry as from septic tank discharges, and recreational pressures such as rock climbing.

A parasitic fly Dionaea aurifrons - The larvae of this very rare and bristly sand dune fly are parasites of spurge bugs Dicranocephalus. The adults are on the wing from May to August, on flowers of ragwort and of spurges. It was found at Braunton Burrows in August 2016. Here it is threatened by scrub invasion and lack of mobile sand.

Image above by Andrew Cunningham
Bog hoverfly Eristalis cryptarum - This extremely rare hoverfly is now only known in the UK from a few mires and bogs on Dartmoor, having been lost from sites elsewhere in the UK. The attractive yet elusive adults nectar on the flowers of marsh marigolds, bog-bean and devil's-bit scabious. Its larvae have not yet been found but will be aquatic and have long breathing tubes ("rat-tailed"). It is threatened by a lack of understanding of its larval ecological requirements, and so perhaps by changes in hydrology, water chemistry, livestock grazing and scrub invasion.

Image above by Rob Wolton
Lagoonal sea-snout cranefly Geranomyia bezzii - The larvae of this rare cranefly are unusual in feeding on tidal mud flats on green algae. The adults, which are poor fliers, shelter in low-growing bushes such as those of sea purslane just above high water mark. It is vulnerable to coast defence works, changes in water quality and probably rising sea level.

Image above by Rob Wolton
A cranefly Helius hispanicus - This long-snouted cranefly in known in the British Isles only from two or three seepages running down the coastal cliffs of the Axmouth to Lyme Regis Undercliffs, close to Axmouth Harbour. Here is threatened by cliff-stabilisation works, by changes in hydrology, and by septic tank discharges from properties above.

Least cigar-gall fly Lipara similis - This rare fly is dependent on reed beds, the larvae developing in galls on the stems of common reed. Otherwise known from a few sites in East Anglia, it has recently been found in at two sites in Devon, the Axmouth -Lyme Regis Undercliffs and the Exe Estuary, as well as one in the New Forest. At the Exe Estuary it occurs both in the tidal reedbeds at the head of the estuary and in the Old Sludge Beds nature reserve. Another, even rarer, fly of the same family, Cryptonevra consimilis is dependent on the galls caused by L. similis. It has been found at the Exe Estuary. Both flies are threatened by loss of reedbed through scrub invasion or rising sea levels.

Image above by Rob Wolton
A totem hoverfly Sphaerophoria potentillae - This small yet attractive hoverfly is rare throughout Europe and known only from only three locations in the UK, two of which are SSSI Culm Grassland sites in North Devon (Beaford Moor and Common Moor (West Putford)). Here is associated with tussocky purple moor grass beside small runnels. It has not been found on well-grazed or frequently burnt sites. The larval biology is unknown. The fly is threatened by pond creation, heavy cattle grazing, scrub invasion and probably winter burning. Further research into its precise habitat requirements is needed.

Further sources of information:

The Dipterists Forum

Cranefly Recording Scheme

Hoverfly Recording Scheme