Woodland hosts a phenomenal number of flies, many of which are very attractive, some of which prey on other invertebrates and a few of which can bite humans painfully. Most of the soldierflies and their allies are shown in the Gardens section of this website, but there are plenty of other families to show here. St Mark's-flies (Bibio marci, 11mm), given the name because they are usually seen around St Mark's day (25 April), are by no means predators. Their larvae feed on roots and vegetable matter underground and they are valuable pollinators of fruit trees. However, 2005 saw a massive emergence of the species, which made it open season on them for predators.
The most active of these were empid flies, led by Empis tessellata (12mm), which are powerful hunters. They are less prone to cannibalism than robber-flies but a male finding a female feeding is on pretty safe ground as to his own safety when pairing.
One nationally scarce fly which I was lucky to find and photograph mating close to some ancient woodland is Megamerina dolium (12mm), a fairly long, dark fly with red legs which is associated with dead wood habitat. Larvae have been found under the bark of fallen trees. Females have appeared in m grden in 2014 and 2015, suggesting the local area is good for this fly.
Megamerina dolium is nationally scarce and the same goes for Micropeza lateralis (10mm), a stilt-legged fly which seems to have an association with broom bushes. Also scarce is Chetostoma curvinerve (8mm), a picture-winged fly in which the male has a definite moustache. The species is possibly an inquiline in sawfly galls and is seen quite late in the year, in November and December.
Fannia lustrator (8mm) is from the Fanniidae or lesser housefly family. Males gather in swarms beneath trees and their hovering is impressive. The larvae of snail-killing flies in the Sciomyzidae family prey on gastropods and are often found near water. They can have impressive banded eyes and mottled wings, and Coremacera marginata (10mm) illustrates this perfectly. It is often found at woodland edge and is quite common.
Flesh-flies (Sarcophaga carnaria, 12mm) are also scavengers which breed in carrion or dung. The female does not lay eggs but live maggots.
Tachinid flies are not predators but parasites. Eriothrix rufomaculata (12mm), Dexiosoma caninum (12mm), Nowickia ferox (14mm) and Tachina fera (15mm) are all striking physically. Larvae of Eriothrix rufomaculatus, Nowickia ferox and Tachina fera feed on moth caterpillars. Dexiosoma caninum, nationally widespread but seen only a handful of times in Surrey, is believed to use chafer beetle larvae. Mintho rufiventris (10mm) resembles Eriothrix rufomaculatus but is altogether less common. Another tachinid, Phasia hemiptera (8mm), lays eggs on bugs, in particular the Forest Bug and Green Shieldbug.
Eustomalyia hilaris (11mm) is another parasite but one that uses the nests of digger wasps, especially Ectemnius cavifrons, in which to lay her eggs. This is not a common species and one I saw in my garden in 2012 was only the fifth record in the county.
Ensign flies are two a penny but might not be noticed since they are tiny. They are also highly active and keep the wings open and quivering when settled. They may be found almost anywhere but they rely on mammal faeces for their life cycle. Common again and with a similar background - their larvae feed on dung - is the Noon Fly (Mesembrina meridiana, 11mm). This is seen for much of the year, often on flower heads.
The Lauxaniidae family are usually small and often dumpy flies. The larvae have various food sources, including leaf litter, the soil, rotten wood, leaves that are mined and birds' nests. Two examples are Minettia inusta (5mm) and Minettia longipennis (5mm). Neurigona pallida is one of the Dolichopodidae or long-legged flies. It has an association with dead wood and is not widely recorded in southern England.
The Yellow Dung-fly (Scathophaga stercoraria, 10mm) is not a robber-fly and can be seen swarming around the mammal dung on which their larvae feed. They are effective hunters of fair-sized prey, and when they have finished the scavenging a Scorpion Fly (Panorpa communis, 14mm) can move in, as happened with those pictured on this page.
These common insects, with the male having the end of the abdomen turned up scorpion style, will feed on almost anything from rotting fruit to bird droppings. They are related to Lacewings and, like them, prefer shade to sun. Scorpion Flies are Mecoptera whereas Snake Flies such as Phaeostigma notata (15mm) are Neuroptera. Their English name comes from the length of the neck and the female uses her long ovipositor to lay eggs in the bark of dead or decaying trees, where the larvae dine on beetle grubs.
Images © Jeremy Early. All rights reserved.
In 2013 I published My Side of the Fence - the Natural History of a Surrey Garden. Details may be found, and orders placed, via this hyperlink My Side of the Fence. In November 2015 Surrey Wildlife Trust published the atlas Soldierflies, their allies and Conopidae of Surrey, jointly written by David Baldock and me. Details are on this web page: Atlas.