How do aquatic insects keep a grip on the bottom in fast water?

Good question!  Find out below

Top: A net-winged midge larva sits comfortably on the top of a large rock in fast water.  As for getting washed away in the swift current in has little to worry about.  Hidden on the underside of it’s abdomen are six disc shaped suckers to grip the rock with (Left photo).

Brachycentrus larvae feeding.  They attach their cases to the tops of rocks with silk threads.

Drunella doddsi nymph showing the pile of fine hairs on the underside of its abdomen.

Epeorus nymph.  Note the large overlapping gills that create a suction cup like grip on the bottom.

Rhithrogena nymph.  Gills similar to those on Epeorus.