Caddisfly, line drawing.
- Andrew Howells
- © Australian Museum
Caddisflies belong to the Order Tricoptera
What do caddisflies look like?
- 2 mm - 40 mm.
- Long and usually widest at wing attachment (wide shoulders), abdomen tapers.
- Very hairy.
- Appears soft and fragile.
- Thread-like with many segments.
- Longer than half its body length, to much longer than the body.
- Large, bulging and well separated.
- Ocelli (tiny single lens eyes) often visible on top of head.
- Reduced and mostly non-functional, if functional they are for ingestion of fluids.
- Palps (mouthparts that look like a chain of beads) usually long and visible.
- Two pairs.
- Both pairs covered in hairs include the membranous regions of the wing.
- Both pairs are membranous and partially see-through due to either pigmentation or numerous hairs.
- Both pairs have few cross-veins forming at most long rectangular cells.
- Hindwing shorter and wider than the forewing.
- At rest wings are held tent-like or rarely flat over body.
- Six legs.
- Hairy, slender and often with paired spines at joints.
- Cerci (tails) absent.
- Maybe modified with male reproductive parts.
Where are caddisflies found?
- Close to water on rocks, among plants and under overhangs.
- Some are coastal marine species.
What do caddisflies do?
- Caddisflies often group together in mating swarms.
- When disturbed they fly away but may travel only short distances.
- They are awkward fliers with a rapid wing beat. They tend to fly in a kind of circular motion and usually in short bursts.
- They often perch with head facing upwards.
- Adults are short-lived, do not feed, or at most ingest fluids.
- They are active during the night or day, night-active species are often attracted to light.
What looks similar?
- Moths are often confused with caddisflies. Moths never have the extremely long antennae that many caddisflies possess. Unfortunately, distinguishing caddisflies with short antennae from some moth species is very difficult without a microscope. The wings and bodies of moths, unlike caddisflies, are covered to some degree with scales and not hairs. Moths also have mouthparts (when present) that are usually a long curved or coiled pair of tubes. Moths also have ocelli (when present) near the top of their eyes instead of on top of the head.
- Lacewings can be distinguished from caddisflies in most cases, by having wings with numerous cross-veins and forked veins along the wing margin. If lacewing wings are hairy they are only hairy along the veins and wing edges, never on the membranous areas.