Rheotanytarsus Midge Larva Pictures

Here's what lived inside.

Here's a natural view of this specimen still attached to its rock quite tightly. You can faintly see the "corners" on the top of the case, which is not a smooth curve, but is somewhat trapezoidal in cross-section.

I removed the case from its rock to expose this, the underside.

A millimeter ruler overlaid by the case.

I don't think we'll need to be imitating this species anytime soon, but it's still a neat insect.