Black Fly

Scientific Name: order Diptera, family Simuliidae

Black flies are the most important trout food that nobody imitates. Note: this doesn't say black flies are the most important trout food. Just the most important one that nobody bothers to tie flies for.

Black fly larvae are abundant in many running water habitats. They hold on tightly to rocky substrates. Pupation occurs underwater, and the fully-formed adult rises to the surface encased in a silvery bubble of gas. That bubble keeps their wings dry, so black fly adults emerge at the surface and instantly fly away. For this reason, you never see any rise forms during a hatch.

The best fly fishing tactic is to dead-drift a larva pattern through quick flowing, rocky habitat deep enough to hold trout; use tight line nymphing tactics to present a rising adult. You can also cast adult patterns where riffle water starts to slow at the head of a shallow run, but nymphing with a larva pattern is more productive.

There is an excellent two-part article on black flies and their imitations in the Westfly archives.

Characteristics

LARVA COLOR: Smoky gray, dirty yellow, creamish, or black

PUPA SIZE: 3-7 mm (1/8 to 1/4 in)

PUPA COLOR: Silvery case over black adult

ADULT SIZE: 3-7 mm (1/8 to 1/4 in)

ADULT COLOR: Black

OTHER CHARACTERISTICS: Back third of larva is much thicker than front

 

Click on the fly name to see the pattern. Click on the presentation to learn how to do it.

STAGE PATTERN SIZE/
COLOR
PRESENTATION WHERE
Larva Clear Simuliid Larva 12-16
Cream, white, dirty yellow
indicator, tight line riffles, just below riffles
Beadhead Simuliid 12-16
Cream, white, dirty yellow
indicator, tight line riffles, just below riffles
Mini Black Fly Larva 18-22
Black
indicator, tight line riffles, just below riffles
Pupa Rising Black Fly 12-16
Black
indicator, tight line, rising nymph riffles, just below riffles
Adult CDC Sleepy John Estes 12-16
Black
standard dry fly runs and tailouts below riffles, bankwater