Black Gnat
Bibio johannis — Black Bibio, Blue Black Gnat
A ubiquitous summer terrestrial — the Black Gnat is available to fish on virtually every European river when other hatches are quiet.
Terrestrials — Terrestrial
Bibionidae
Body 5–8 mm / Hook size 16–18
All day when present (terrestrial)
Universal — any watercourse adjacent to vegetation
Lifecycle
Bibio johannis is a member of the Bibionidae family and shares its terrestrial lifecycle with the Hawthorn Fly. The larva lives in soil and decaying vegetation. Adults appear in late spring and summer, remaining present throughout the summer. They fly low over vegetation and individuals regularly fall into the water.
Peak months
The Black Gnat is the summer dry fly fisher's constant companion — not dramatic like the Green Drake, not technically demanding like the Caenis, but reliably present and reliably taken throughout the summer.
Fishing tips
Under the Trees
Target the shaded runs under overhanging alders, willows, and hawthorn. Fish lie in the cooled water in summer heat and feed opportunistically on insects falling from branches above.
Fly patterns
Other hatches
MayfliesBlue Winged Olive
Serratella ignitaThe most important small olive on British and European chalk streams — reliable, widespread, and technically demanding.
Midges & DipteraBuzzer / Midge
Chironomidae sp.The most important insect of all on stillwaters — year-round, in every month, on every productive lake and reservoir in Europe.
MayfliesCaenis
Caenis horariaThe infuriatingly tiny mayfly that hatches in such vast numbers that fish refuse to look at anything larger — the tying and presentation challenge of a lifetime.
CaddisfliesCinnamon Sedge
Limnephilus lunatusA common summer evening caddis found across Europe — its reliable evening hatches from June to August provide consistent dry fly fishing.
TerrestrialsCommon Cockchafer
Melolontha melolonthaDuring evening flights, heavy beetles fall onto water and become high-value mouthfuls for surface-feeding fish.