Analysis of information sources in references of the Wikipedia article "Mayfly" in English language version.
It has been advanced as an argument against the use of the wet fly, that duns and the other small insects which drift down upon the surface of a stream are never seen by the fish under water, and that a wet fly is therefore an unnatural object, especially if winged. "Never " is a big word, and I venture to think the case is overstated. I have watched an eddy with little swirling whirlpools in it for an hour together, and again and again I have seen little groups of flies caught in one or other of the whirls, sucked under and thrown scatterwise through the water.
Regional colloquialisms include fishflies, shadflies, and a slew of other names that aren't fit to print.