HOMES AND GARDENS - SOLDIERFLIES AND ALLIES





 

 

Soldierflies and their allies, or the ‘Larger Brachycera’, consist of 11 families of fly that differ markedly in colour, size and life cycle. The families are Soldierflies (Stratiomyidae), Horseflies (Tabanidae), Robberflies (Asilidae), Snipeflies (Rhagionidae), Stiletto-flies (Therevidae), Bee-flies (Bombyliidae), Hunchback-flies (Acroceridae), Water-snipeflies (Athericidae), Awl-flies (Xylophagidae), Windowflies (Scenopinidae) and Wood-soldierflies (Xylomyidae).

There are 159 species in Britain, some of which are found only only in the North or the West, and a number of which are coastal. Many require wetland and a good number of the soldierflies are associated only with that habitat. Generally the soldierflies and their allies are quite hard to find and a high proportion have a conservation designation. In November 2015 Surrey Wildlife Trust published the atlas Soldierflies, their allies and Conopidae of Surrey, written by David Baldock and me. This covers the 103 (now 104) species found in the county and details are available here: Atlas.

Three-quarters of the flies shown on this page were recorded in my garden in Reigate between 2013 and 2016. Three others, the Banded General (Stratiomys potamida), Black Colonel (Odontomytia tigrina) and Black Snipefly (Chrysopilus cristatus), are shown in the Wetlands section and four more are in the Heathland pages. These are the BAP species Hornet Robberfly (Asilus crabroniformis) and Mottled Bee-fly (Thyridanthrax fenestratus) and the scarce Golden-tabbed Robberfly (Eutolmus rufibarbis) and Spring Heath Robberfly (Lasiopogon cinctus).

The number seen in the garden shows how study of a local habitat can reveal unexpected gems in unexpected places – a fair percentage were noted on cherry laurel leaves, or undeneath them. This is a plant which has a poor reputation among willdife watchers but clearly it is not all bad, perhaps in part because of the nectaries under the leaves. The highlights were discovering the Drab Wood-soldierfly (Solva marginata, 6mm) and Silver-strips Black (Neopachygaster meromelas, 3mm) breeding in Grey Poplar logs placed in a pile after a tree was blown down in December 2013. Then a Long-horned Cleg horsefly (Haematopota grandis, 13mm) appeared in my gazebo in September 2015. This is a Red Data Book 3 species recorded only very rarely away from the coast; the record was the first for Surrey.

One of the smallest groups of soldierflies are the Pachygastrinae, including the Silver-strips Black. Others in this subfamily are the Dark-winged Black (Pachygaster atra, 4mm), the Yellow-legged Black (Pachygaster leachii, 4mm) and the Scarce Black (Eupachygaster tarsalis, 4mm). The last-named had not been recorded as an adult in Surrey until the pictured specimen was taken in my garden in 2014.

Many other soldierflies are much more colourful, notably the Broad Centurion (Chloromyia formosa, 8mm), which shows sexual dimorphism and is a summer species with a liking for umbellifer flowers, and the Twin-spot Centurion (Sargus bipunctatus, 12mm), which does not appear until September most years and can continue flying until November.

Beris species are medium-sized and do not usually advertise their presence. The commonest nationally is the Murky-legged Black Legionnaire (Beris chalybata, 6mm) but in the garden it is easier to find the Yellow-legged Legionnaire (Beris morrisii, 7mm). One of the most attarctive is the Common Orange Legionnaire (Beris vallata, 7mm), with its attractive bright orange abdomen. The Bright Four-spined Legionnaire (Chorisops nagatomii, 7mm) was recognised as a species only quite recently but is widespread. The same applies to a soldierfly frequently found on foliage in gardens, the smart green Black-horned Gem (Microchrysa polita, 5mm).

Snipeflies are not that colourful, although some have red or orange markings, and a number are quite small. Despite fables to the contrary, they are not blood-suckers in the UK or predators anywhere. The Rhagio and Chrysopilus genera are the most frequently found, with the Marsh Snipefly (Rhagio tringarius, 10mm), Downlooker Snipefly (Rhagio scolopaceus, 10mm) and Small Fleck-winged Snipefly (Rhagio lineola, 7mm) not difficult to find. Rhagio lineola is pretty small but is still larger than the Little Snipefly (Chrysopilus asiliformis, 5mm). The Tree Snipefly (Chrysopilus laetus, 8mm) is the rarest of the genus and was designated Endangered in the Red Data Book in the 1980s. However, it is expanding its range, perhaps in part because of the effects of the storm of 1987, and a female appeared on an oak stump in my garden in July 2016. She had been egg-laying; the species is suited by old woodland including beech and poplars.

Robberflies are mostly quite drab in colour and are remarkable predators. I do not get that many in the garden but the Stripe-legged Robberfly (Dioctria baumhaueri, 10mm) has been noted taking a Silver-strips Black, a solitary bee, a beetle and an ichneumonid. This is a common species, as are the Violet Black-legged Robberfly (Dioctria atricapilla, 10mm) and the Common Red-legged Robberfly (Dioctria rufipes, 10mm). A much scarcer Dioctria species is the Scarce Red-legged Robberfly (Dioctria cothurnata, 12mm), one of the largest of the genus but found in only one small area in Surrey around Brookwood Cemetery and in few other places in lowland England.

A common species throughout the summer is the Kite-tailed Robberfly (Machimus atricapillus, 13mm), which can turn up almost anywhere – one spent time sunbathing on a metal pole supporting my gazebo two days running in 2014. Not quite so readily found is the Brown Heath Robberfly (Machimus cingulatus, 11mm), a species of sandy heathland that hunts mostly Diptera (flies) from bracken, heather, bare ground or dung. It is essentially southern, peaking in August but found until October in good years.

The Common Awl Robberfly Neoitamus cyanurus, 15mm) is large and lives in woodland where – uniquely in the family – it habitually hunts moths. The English name comes from the very long ovipositor, as shown in the image. The Golden-haired Robber (Choerades marginatus, 12mm) is also species of woodland, principally oak woodland. It has strong mandibles and records of prey taken include a leafhopper bug and beetles, among them a weevil. In contrast, the Striped Slender Robberfly (Leptogaster cylindrica, 12mm) occupies grassland. This species combines being lengthy with being thin.

Stiletto flies are named for their knife-like shape, and the Common Stiletto (Thereva nobilitata, 12mm) lives up its name by turning up frequently. Stiletto flies are scavengers, not predators.

Horseflies are among the least popular of all Diptera given the way they suck blood from people as well as mammals. A number of our species are coastal in distribution and with the exception of Haematopota grandis (see above) I have not been able to find and photograph a large number to date. The Notch-horned Cleg (Haematopota pluvialis, 10mm) is the commonest horsefly in Britain. The Band-eyed Brown Horsefly (Tabanus bromius, 13mm) is not difficult to find. As the name suggests, the Dark Giant Horsefly (Tabanus sudeticus) is altogether larger. The pictured female, which flew into the bathroom of a guest house while I was showering, measured 25mm from face to tip of abdomen. This species is much commoner in northern and western Britain than in the south.

The Splayed Deerfly (Chrysops caecutiens, 11mm) and Twin-lobed Deerfly (Chrysops relictus, 11mm) both have remarkable eye colouring, with red, green and purple mixed together. The deerflies aim for the head of humans and are easy enough to hear when they approach.

With one exception, the species on the British list of bee-flies are not common. Lowland England has the bulk of populations of the Mottled Bee-fly and has prodigious numbers of the Common Bee-fly (Bombylius major, 12mm). This species has a long proboscis, enabling it to nectar from a wide variety of flowers, and is a parasitoid of solitary mining bees. Large numbers of eggs are laid from mid-air and the aim is for some of the resulting larvae to find active nests. The speculative tactic appears to work since this species is doing pretty well.

In addition to the Tree Snipefly, 2016 brought another new species to the garden in a male Common Awl-fly (Xylophagus ater, 9mm), seen on dead wood in the spring. This species is elusive with a long life cycle of around three years. It is associated with old woodland – the larvae feed on other invertebrates in decaying timber – and the park behind my garden offers a suitable habitat.

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.

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