Bibio marci - Hawthorn Fly and Bibio pomonae - Heather Fly

Phylum: Arthropoda - Class: Insecta - Order: Diptera - Family: Bibionidae

Hawthorn Fly on Gorse

On sunny spring days, hawthorn flies flit across meadows, along the hedgerows and among low bushes. Instantly recognisable by their long trailing hindlegs, these swarthy flies hatch in their millions and sometimes cause concern when they arrive in people's gardens. They are in fact non-biting and do not sting. If there is a good breeze, particularly on exposed upland streams and lakes,considerable numbers of Hawthorn Flies end up on the surface of rivers, streams, reservoirs, lakes, ponds and canals.

A mating pair of Hawthorn Flies

In waters containing trout, grayling or other kinds of fish that feed on floating insects, Hawthorn Flies are usually the first of the terrestrial insects to cause a worthwhile rise.

The large female hawthorn flies begin hatching around St Mark's day, which is 25th April, although their smaller mates are sometimes seen a week or so earlier. The hatch is generally over by mid May.

Mating Hawthorn Flies

In the picture above you can see how much larger the female (on the left of the picture) is than the male (seen on the right).

In meadowland you will often see swarms of Hawthorn Flies rushing about just above head height. Once on the water, it is rare for a Hawthorn Fly to escape the attention of feeding trout.

John Beer's imitation Hawthorn Fly
Hawthorn imitation (Jon Beer)

This simple but very effective pattern was devised by Jon Beer, for whom the Hawthorn Fly is a firm favourite. The hook is a size 14.

Heather Fly Bibio pomonae

Heather Fly Bibio pomonae

Very similar to the Hawthorn Fly, dut distinguished by it red thighs, is the Heather Fly, a summer terrestrial insect that also gets blown on to upland lakes and rivers. Use the same artificial fly to imitate Hawthorn Flies and Heather Flies; trout won't be able to see the difference!.

Fishing tip

Although stillwater trout will sometimes take a 'retrieved' hawthorn fly fished just below the surface, dry fly tactics are usually best when tackling river trout and 'educated' stillwater trout.

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