Bibio johannis - Black Gnat

In spring, and again in autumn, black gnats can be seen swarming near the surface. Although the spring and autumn flies are not the same species, they are so similar that for angling purposes we can treat them as one.

For the lake fisher, the black gnat is an insect of the margins, often preferring the shade beneath overhanging trees. Any darkish dry fly of the right size (16 or 18) is usually acceptable provided it is fished on a fine leader.

On rivers and streams, black gnat clouds are frequently densest over the slower sections. Mating pairs are particularly vulnerable in blustery weather and fall to the surface, where the trout are only to pleased to consume them.

Matching the hatch

Many black gnat patterns are available, including the Knotted Midge which imitates the mating pair. This useful pattern was devised by Peter O'Reilly. Unlike some shop-bought 'black gnats' it has, quite rightly, no tail. The hook is a size 16.

Fishing tip

If you have difficulty trying to keep sight of tiny dark flies such as this as they float on the dark surface of the water, try adding a pair of white wings. (Tie them swept back along the fly, not upright.) The result is a 'bi-visible' fly.

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