Caseworm, AKA Caddisfly Larva

Subject: Water hermit insect
Location: British Columbia, Canada
April 8, 2016 5:34 pm
Found this bug in the water. It likes to flap it’s long body to get around as if someone tied it to a chair. It’s quite hilarious. Wondering what it’s diet is as well. It seems to have a long body and white (mini legs) along its body which is noticeable when it comes out to swing itself around. Kind of reminds me like a wormlike-roach in water but I really don’t have an idea what this creature is. Thanks!
Signature: R.


Dear R.,
This is a Caseworm, the aquatic larva or naiad of a Caddisfly, a mothlike insect from the order Trichoptera.  According to BugGuide:  “The aquatic larvae have three pairs of legs and a soft, elongate, segmented abdomen usually hidden inside a case; head well-developed with chewing mouthparts in most species.  Most species live in a mobile case constructed from plant material, algae, grains of sand, pieces of snail shells, or entirely of silk. The case is held together with strands of silk secreted by the larva. In some species the case is attached to a rock, log, or other underwater surface; a few species have no case and are free-living.  The case’s particular shape and construction material is distinctive of the family and/or genus, and can be used in identification. Example: Helicopyschidae larvae use sand grains to build spiral cases that resemble small snail shells.”


Wow, neat. Thanks for your response Daniel!

2 thoughts on “Caseworm, AKA Caddisfly Larva”

Leave a Comment