What Color Are Leeches? ID Guide + Fly Patterns

Description

Leeches are segmented worms (Class Hirudinea) that are synonymous with big fish. Predatory and omnipresent, leeches live in almost every body of water that holds trout: lakes, ponds, spring creeks, and freestone rivers. While many people associate them with blood-sucking, many aquatic leeches are scavengers or predators of small invertebrates. For the fly angler, "The Leech" is one of the most effective streamer patterns in existence (e.g., the Woolly Bugger). A swimming leech represents a substantial, calorie-dense meal that triggers aggressive strikes.

Life Cycle Stages

Adult

There is no metamorphosis. Baby leeches look like small adults. Appearance: Elongate, segmented, ribbon-like bodies. Can expand and contract significantly. Colors: Black, Olive, and Brown are the "Big Three." Some are mottled or have reddish hues. Movement: They swim with a mesmerizing, undulating ribbon motion.

Recommended Fly Patterns

Woolly Bugger

#4-#10

Olive, Black, Brown, White

Pine Squirrel Leech

#8-#12

Black, Natural, Olive, Rust

Autumn Splendor

#4-#8

Brown/Yellow/Orange, Fall Colors

Thin Mint

#6-#10

Black, Brown, Olive

Bunny Leech

#6-#12

Black, Olive, Brown, Purple

Egg-Sucking Leech

#6-#10

Purple, Black, Orange, Pink

Habitat

Leeches prefer slower water, weedy areas, and soft bottoms, but are found in river pools and lake margins everywhere. They hide under rocks, logs, and vegetation during the day and become more active in low light.

Behavior

Leeches are nocturnal or crepuscular (active at twilight). This makes them fantastic patterns for early morning, late evening, or cloudy days. In lakes, they cruise the weed lines. In rivers, they get swept from the banks during high water or swim in the deep pools. The "Balanced Leech" technique (suspending a leech under an indicator) is deadly because leeches often hover or swim slowly rather than stripping fast.

Fishing Information

Seasonality Year-Round. Essential for Ice-Out on lakes and Spring runoff on rivers.

Tactics

The Strip: Strip a Woolly Bugger or Mohair Leech with a pulse to mimic the undulation.
Dead Drift: In rivers, a dead-drifted leech (often micro-leech size #10) under an indicator catches tons of fish.
Balanced Leech: On stillwaters, suspend a balanced leech under a bobber. The wave action gives it a natural jigging motion.
Colors: Black is best for low light/muddy water. Olive/Brown for clear water.
Attractor: Many "Egg Sucking Leech" patterns combine a leech body with a bright color trigger.

Recommended Patterns