A Trio Of Bibios

Les Lockey highlights the importance of the Bibio throughout summer, sharing his successful imitations on Scotland’s Coldingham Loch.

Here in the UK, the Bibionidae family of terrestrial flies contains 18 species, three of which, the hawthorn fly (Bibio marci), black gnat, (Bibio johannis) and heather fly (Bibio pomonae), are of particular interest to the still water fly angler. Characteristically, these flies are generally black and hairy, although some are distinctly red in parts. Varying in size from about four to 15 millimetres in length, the sexes differ substantially in appearance, with males having large, bulbous eyes and pale shiny wings. Females by contrast are larger, but have very small heads, tiny eyes and usually darker, less shiny wings, but, importantly for the fly angler, trout feed on them avidly.

St Mark’s Fly

The hawthorn fly, also known as St Mark’s fly, because they usually hatch around April 25th (St Mark’s day), are the largest members of the Bibionidae family. They emerge synchronously over just a few days in spring, producing an abundant but somewhat short-lived bounty for hungry trout. Curiously, it is only the males, with their distinctive trailing legs, that form the conspicuous flying swarms usually seen around flowering shrubs and hedgerows. However, they are not strong fliers and are easily blown onto the water, invariably creating the first major fall of terrestrial flies in the still water fly fishing year.

Often, the most effective way of tackling any fall of terrestrial flies is from a boat with an appropriate dry-fly imitation, which is always my preferred option. A standard 9ft 6in 6-wt rod, coupled to a Scientific Anglers Mastery MPX floating line and a 14ft fluorocarbon tapered leader with a single dropper is my standard dry-fly setup. For hawthorn-feeding fish, a small black Hopper on the dropper with a CDC Winged Hawthorn imitation on the point have worked consistently well for me. However, once the trout have locked onto the naturals, just about any black, bushy dry will do.