A trout recently caught by Graham Steart in KZN was full of the bugs he photographed below.
Click to enlarge
He thought they must be an aquatic species, but wasn’t sure. I thought they may either be an aquatic form of the bug family Hemiptera or, more likely given the absence of legs, maybe a mayfly nymph of the Prosopistomatidae family, but I was guessing.
Herman Botha thought they were water mites, an arachnid species, but I think Martin Rudman has hit the nail on the head. He believes that the ‘mystery insects’ are called water pennies, a lovely and apt name.
Of the Family Psephenidae, they are the larval form of a beetle and are usually found clinging to the bottom of rocks in streams and rivers. Trout are known to forage them off the stones, though they are probably not worth imitating.
Below is a link to more images of water penny adults and larvae.
