This common name refers to only one class.
Nearly a million species of insects have been described by entomologists. I have left several of them off of this site, just to save time, but I've tried to include all the main aquatic insects trout eat in North America.
This site focuses on aquatic insects, of which the most important are mayflies (Ephemeroptera
) and caddisflies (Trichoptera
). Stoneflies (Plecoptera
) come in third, a position arguably challenged by the many two-winged true flies of the Diptera
order, which includes midges and craneflies. I've also included some terrestrial
insects which I've found on or near trout streams. Terrestrials
like ants, beetles, and grasshoppers are an important food source for trout in many places, especially during the summer months.
Aquatic insects do not live their entire lives in the water. Instead, they grow for a year (give or take quite a bit) as nymphs or larvae underwater, and then they emerge into air-breathing winged insects for a short while to mate and die. There are many variations on this theme.
The most important aquatic insects for fly fishermen are mayflies, stoneflies, caddisflies, and midges. Mayflies and caddisflies are the most discussed by angler-entomologists, because it's so useful to closely identify them. The behavior of their species guides the behavior of feeding trout, and an angler who understands the lifecycle of a particular species has the upper hand when it's hatching. This is not so important for stoneflies and midges, because their hatching behavior is less variable.