What does caddis mean?
Caddis is the common name for members of the order Trichoptera, small, moth-like insects best known for their aquatic larvae, often called caddisworms, which construct remarkable portable cases from sand grains, pebbles, twigs, and silk. The word appears frequently in two settings: entomology, where it labels the insect and its larva, and angling, where 'caddis' refers to the natural hatch as well as the artificial flies tied to imitate it — patterns that are staples of any trout fisher's box. Because adult caddisflies resemble drab moths and are most active at dusk near water, they are less conspicuous to the general public than mayflies, yet they are among the most widespread freshwater insects, found in streams, rivers, and lakes worldwide. The term carries no strong connotations beyond its specialist associations; it is a plain, functional label whose charm lies in the extraordinary engineering of the creatures it names. For readers interested in freshwater ecology, fly tying, or simply the ingenuity of animal builders, 'caddis' is a rewarding word to know.
nounA caddis is a caddisfly, a small moth-like insect of the order Trichoptera, or more commonly the protective case its aquatic larva builds from sand, gravel, and plant debris.
- An insect of the order Trichoptera (a caddisfly), especially in fly-fishing contexts where it refers to the natural or artificial imitation of the insect.
- The aquatic larva (caddisworm) of the caddisfly, which builds a protective case around itself.
"The trout were rising steadily to feed on the caddis drifting along the streambed."
"In late spring the river came alive with hatching caddis, and every trout in the pool rose to take them."
"Under the overturned stones we found dozens of caddis cases, each one assembled from tiny fragments of gravel and leaf."
When referring to individual insects or larvae, the plural 'caddises' is used; anglers typically speak of 'caddis' as a mass term.
"Several caddises clung to the rocks beside the weir."
Caddis larvae are nature's architects: they glue grains of sand and tiny twigs into portable houses, and artists have even coaxed captive larvae into building cases out of gold flakes and jewels.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of caddis
The word 'caddis' first appears in English in the sixteenth century, originally as a name for a kind of woolen or worsted ribbon or braid, and was later applied to the insect's larval case, whose texture reminded people of that fabric. The ultimate origin of the earlier sense is uncertain, though it has been linked to French dialect words for ragged or shaggy material. The connection to the insect arose from the resemblance between the larva's fibrous case and this coarse woolen cloth, giving English one of its more curious examples of a textile term becoming an entomological one.
Related word forms
How caddis is actually used
Most familiar among anglers and entomologists; outside these circles the full form 'caddisfly' is more common than the clipped noun 'caddis'. In fly fishing, 'caddis' often denotes both the natural insect and the artificial fly tied to imitate it.
Easily confused with caddis
A 'caddy' is a container for tea or an assistant in golf, whereas a 'caddis' is an insect or its larval casing.