Identification

Adult caddis flies have two pairs of wings which are covered in tiny hairs; this along with the presence of biting mouthparts, distinguishes them from moths, which have scaled wings and a long proboscis. The wings are held tent like over the body when at rest.

Caddis flies go through complete metamorphosis. Most have aquatic larvae, which have well developed jaws and legs. The larvae are usually covered by a protective case made of materials such as grains of sand, snail shells or plant material, held together by silken threads. Some caddis fly larvae make their case from silk, and others have no case at all. Most larvae are omnivorous, feeding on both plant and animal matter.

The pupal stage takes place within the larval case which is cemented to a solid object underwater. When pupal development is complete the mobile pupa releases itself from the case and floats to the water surface, where the adult emerges. The adults are able to fly immediately after exiting the pupa Many caddis flies do not feed as adults, those that do probably feed on nectar and pollen.

Size

Body lengths from under 2 mm to 20 mm.

Distribution

Everywhere in the UK, but usually close to an aquatic habitat.

Status

Over 6000 species of caddis fly have been described worldwide, 190 species occur in the UK. Along with mayfly and stonefly larvae, the assemblage of species can be used to assess the quality of lakes, streams and rivers.

Where to find them in the garden

Caddis flies are more likely to be found in gardens with ponds, or those close to rivers, lakes or streams. The adults fly mainly at night and may be attracted to external lights.

Role in the garden

Caddis flies have no impact on garden plants. The adults are a valuable food source for bats and birds, while fish feed on the emerging adults.