Testate Midge Larva

[Olympusman]

I have been observing Midge larva that make tests for some time but haven't been able to get either a clean specimen or a decent shot. This one showed up in a recent pond dip. I was surprised to find one this late in the season.


Swift 4X 0.10 160/.17 57 shots in Zerene Stacker.

The shape of the tests appears to be specific to the species. For example, this one has a Vee notch at both ends. Some of the red bloodworm larva make a test with long parallel sides that taper toward the ends of the test. Like this test, they are very fine-grained. Some larvae cobble together a test from detritus from the pond.
The larva lives inside the test and wriggles, creating a flow through the test that draws protists into the test to be ingested by the larva. The vortex around the intake end of the test is shaped like a mushroom cap and curls around behind the opening.
When too much clutter builds up around the ends of the test, the larva comes out and cleans up the opening to restore the flow. They are able to curl around inside the test to get to the exhaust end of the test for housekeeping.

[Ichthyophthirius]

Nice photo. I suspect this is a caddis fly larva, probably Family Hydroptilidae. I don't know what genus, but there are a few images here: http://www.flbenthos.org/cgi-bin/cp-app ... richoptera

Cf. Orthotrichia http://urmaskruus.planet.ee/pohjaloomad ... %20sp.html

Ichthy

[Olympusman]

Yep, that test is a perfect match for my specimen. I'll correct my archive. It seems these "tests" appear across a number of species with aquatic larvae. Next spring I intend to finally get some decent images of the bloodworms in their test now that I know how to euthenize them for focus stacking (glutaraldehyde).

[Olympusman]

The wikipedia on caddisflies was very informative. So the fine texture of the case id because they are woven from silk. Interesting. So I may assume the cases made from detrita are held together with silk.