Shadfly vs. Mayfly — What's the Difference?

A mayfly.

Mayflies (also known as shadflies or fishflies in Canada and the upper Midwestern U.S.; also up-winged flies in the United Kingdom) are aquatic insects belonging to the order Ephemeroptera. This order is part of an ancient group of insects termed the Palaeoptera, which also contains dragonflies and damselflies.

A caddisfly.

Any of various delicate, winged insects of the order Ephemeroptera that develop from aquatic nymphs and in the adult stage live no longer than a few days and do not feed.

Mayfly

Any of the many fragile insects of the order Ephemeroptera that develop in fresh water and live very briefly as winged adults.

Slender insect with delicate membranous wings having an aquatic larval stage and terrestrial adult stage usually lasting less than two days

Slender insect with delicate membranous wings having an aquatic larval stage and terrestrial adult stage usually lasting less than two days