Trichoptera - the Caddis or Sedge Flies

This is quite a large order of insects with wings which, when at rest, are held along the body in the form of a ridge tent. A characteristic of flies of this order is the long antennae - in many species more than double the body length.

Great Red
Great red sedge

There are 300 or more species of sedge flies in the British Isles but most are rare, very small or totally nocturnal, so that the number of particular interest to flyfishers is actually quite small.

Life Cycle

There are around two hundred species of sedge flies in the British Isles. Many adult sedge flies are nocturnal. There are, however, some that hatch by day - the Grannom is an example - and many more whose emergence at dusk extends the evening rise. They are found in all sorts of waters from chalk streams and lowland reservoirs to mountain torrents and moorland lakes.

Sedge flies go through egg, larva, pupa and winged adult stages. This life cycle is generally completed in one year, for most of which the insect is in its larval form. The pupal stage typically lasts a month or less and the adults can live for a few weeks.

Larvae

A sedge larva in its case

Sedge flies begin life as caterpillar-like larvae, commonly called caddis grubs. The majority of species live in portable cases which they build from materials gathered from the bed of the stream or lake.

Sedge Pupae

Sedge pupa

When the larva is fully grown, it becomes a pupa. Inside the pupal case the miracle of metamorphosis takes place over a period of several days or a few weeks. When the adult is fully developed inside the pupal shuck, the insect bites its way out of the end of the larval case and swims up to the surface.

Adult sedge flies

Adult sedge fly

Sedge flies have two pairs of wings which, when at rest, are held along the body in the form of a ridge tent. A characteristic of flies of this order is the long antennae - in many species more than double the body length.

When sedge flies return to lay their eggs on moonlit nights a buoyant artificial fly can give great sport.

References

O'Reilly, Pat. (1997; 8th reprint 2010) Matching the Hatch. Shrewsbury: Quiller Publishing.

Barnard, P & Ross, E. (2007) A Guide to the adult caddisflies or sedge flies (Trichoptera). Taunton: Field Studies Council.

Wallace, I. (2006) Simple Key to Caddis Larvae. Taunton: Field Studies Council.

Wallace, I.D., Wallace, B., & Philipson, G.M. (2003) Keys to the Case-bearing Caddis Larvae of Britain and Ireland. Ambleside: Freshwater Biological Association.

Macan, T.T. (1973) A Key to the Adults of the British Trichoptera. Ambleside: Freshwater Biological Association.


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