The hatch chart · Terrestrial
Black gnat
Bibio johannis
- Natural’s size
- Hook 16–20
- Time of day
- Warm, still days
- At its peak
- June, August
- Fly to try
- Black Gnat or Griffith’s Gnat, size 18
The year
- JJanuary: not expected
- FFebruary: not expected
- MMarch: not expected
- AApril: not expected
- MMay: some about
- JJune: main hatch
- JJuly: some about
- AAugust: main hatch
- SSeptember: some about
- OOctober: not expected
- NNovember: not expected
- DDecember: not expected
In the hand
A catch-all name for several small black land flies of 4–6 mm with shining, flat-folded wings. They look like thin houseflies. Mating pairs often fall on the water together.
On the river
Swarms dance over the banks in warm weather and are knocked down by any breeze. Trout taking them rise quietly and often; a small black fly sitting low is all that is needed.