The adult insects sometimes feed on nectar but most are relatively short lived compared to the larval stage and probably do not feed. Some species fly at night and may be attracted to bright lights.
Female caddisflies mostly deposit their eggs into water, sometimes walking down below the surface to place eggs on submerged plants or stones. Limnephilus species often lay batches of gelatinous eggs on plants that overhang water. These eggs are stimulated to hatch during wet weather, when the rain will wash the larvae off the plants into the water below. Most species overwinter as larvae. When the larvae have completed their feeding, they pupate inside silk cocoons or within their cases. When the adult caddisfly is ready to emerge, the pupa leaves the cocoon or case and wriggles to the surface.
Some species of caddisfly have mating assemblies where males cluster together and fly up and down in a column above a fixed point on the ground. Females are attracted to the displaying males and move in to select a partner. Some species emerge and mate in spring-early summer but delay laying eggs until the autumn.
Role of caddisflies in gardens
Caddisflies are part of a healthy garden pond ecosystem. They cause no significant damage to pond plants. Fish will eat the larvae and pupal stages. Night-flying caddisflies can be an important food source for bats during the summer and autumn.
Other sources of information
Barnard, P. & Ross, E. (2012) Handbooks for the Identification of British Insects. The adult Trichoptera (caddisflies) of Britain and Ireland. Royal Entomological Society
Dobson,M. Pawley,S. Fletcher,M. & Powell, A. (2012) Guide to Freshwater Invertebrates Published by Freshwater Biological Association
Edington, J. M. & Hildrew, A. G. (1995) Caseless caddis larvae (Trichoptera). Freshwater Biological Association
Mosely, M. E. (1939) The British caddis flies (Trichoptera). George Routledge & Sons
Wallace, I. D., Wallace, B. & Philipson, G. N. (2003) Keys to the case-bearing caddis larvae of Britain and Ireland. Freshwater Biological Association
Wallace, I. (2006) Simple key to caddis larvae. A Field Studies Council AIDGAP key
Page text drafted by Andrew Halstead, reviewed by Andrew Salisbury, compiled by Steve Head