Pupa
Also called Pupae, Pupal stage
A pupa is the in-between life stage where some aquatic insects transform from larva to adult. In trout fishing, “pupa” usually points to caddisflies and midges as they rise toward the surface to emerge.
- Group
- Life stages
- Category
- Entomology & forage
- Level
- Beginner
- Water
- Freshwater
Last updated
What Pupa means
Some aquatic insects change shape in a pupa stage before they become winged adults. In freshwater, the word comes up most with caddisflies and midges. Mayflies do not have a true pupa stage.
A pupa is often mobile and non-feeding. It often swims or drifts upward in the water column, then emerges into the adult form. That upward movement is why trout and grayling key on pupae during a hatch.
Fly patterns called “pupa” are usually tied to suggest that in-between look and behavior, and often with hints of legs, a wing case, or trapped air. Many are fished under the surface, either dead-drifted or with a gentle lift at the end of the drift.
Why it matters on the water
Knowing what “pupa” means helps you pick depth and motion. If adults are showing but trout are still feeding subsurface, a pupa-style fly in the middle to upper part of the water column often matches what the fish are actually eating.
It also helps you sort out hatch talk. If someone says “caddis pupae are popping,” they are describing the stage just before the adult, which points toward lighter, more mobile patterns than a larva imitation and a presentation that allows a little rise or swing.
Shop Pupa
Read next
- CaddisflyA caddisfly is a common freshwater insect that trout and other fish eat in its larva, pupa, and adult stages. Many species live in streams and rivers, and their hatches can drive steady feeding.
- EmergerA fly that imitates an aquatic insect in the act of emerging, partway between nymph or pupa and a dry fly. It is fished in or just under the surface film, where trout often feed.
- LarvaAn aquatic insect’s immature stage for insects with complete metamorphosis, like midges and caddisflies.
- MidgeA midge is a small two-winged fly; in fly fishing it often means a chironomid. Most of their larvae and pupae live in water. Midges hatch in every month on many rivers and lakes, and trout eat them year-round.