Midge · Aquatic insect
Black Gnat
Bibio johannis
Size
6–9mm
Hook size
#16–14
Hatch window
Season April–OctoberPeak time 11:00–17:00
Water temperature
13° peak
8°20°
Hatches from 8°C, peaking at 13°C, tailing off by 20°C.How fish feed on it
The adult midge matters far less than the pupa did, which is worth knowing before you spend an evening on it. Once it's up and dry it mostly leaves, and trout that were hard on ascending pupae an hour earlier will ignore the finished article. The exception is the egg-layers coming back to the water, and the spent ones lying in the surface film afterwards — both worth a look when fish are sipping in flat calm and nothing else explains it.
Flies that imitate this
Black Gnat
Griffith's Gnat
Coch-y-bonddu
Ecology
Where you'll find this
- British IslesCommon
- Atlantic fringeOccasional
- ScandinaviaOccasional
- Continental EuropeOccasional
- The AlpsScarce
Common Occasional
Identification
Bibio johannis is a species of fly in the family Bibionidae. It is found in the Palearctic....