Caddisflies

Definition

An order (Trichoptera) of holometabolous insects whose larvae are almost exclusively aquatic and adults are terrestrial. Adults are small, moth-like insects with two pairs of hairy, membranous wings held roof-like over the body at rest; they lack the scaled wings of Lepidoptera, their sister group within the superorder Amphiesmenoptera. Larvae are ecologically diverse: Integripalpia larvae construct portable protective cases from sand, plant material, or other debris and forage actively, while Annulipalpia larvae build fixed retreats of silk and debris from which they filter-feed or capture prey. The third suborder Spicipalpia has uncertain affinities and may not be monophyletic.

Etymology

From Middle English 'cadice,' meaning wool or cotton, referring to the silky larval cases; the suffix '-fly' follows standard entomological convention.

Example

Hydropsychidae (net-spinning caddisflies) are Annulipalpia that spin silken capture nets across stream riffles to filter organic particles from flowing water, while Limnephilidae (case-making caddisflies) are Integripalpia that drag their spiral cases of leaf fragments across the streambed while grazing periphyton.

Synonyms

• Trichoptera
• sedge-flies
• rail-flies

Related Terms

• Amphiesmenoptera
• Lepidoptera
• Integripalpia
• Annulipalpia
• Spicipalpia
• aquatic insects
• lotic ecology
• benthic macroinvertebrates
• EPT index

Usage Notes

The common name 'caddisfly' properly refers to the order Trichoptera, not to individual families or species; 'sedge-fly' is preferred in angling contexts. The hairy (not scaled) wings are the key diagnostic feature distinguishing adults from moths. Larval cases are often genus- or family-specific in construction material and architecture, making them useful for field identification. Caddisfly larvae are critical bioindicators of water quality and are staple food resources for fish, especially salmonids.