A fly consists of various materials tied onto – or “dressed” on – the shank of a hook. Common fly-tying materials include furs, feathers, chenille, Mylar, tinsel and colored thread. In trout fishing, there are four main types of flies – dry flies, wet flies, nymphs and streamers – and literally thousands of specific fly patterns.
Fly size directly corresponds to hook size. A size 14 Adams is simply an Adams pattern tied onto a size 14 hook. If you’re unfamiliar with hook sizes, just remember this: the higher the number, the smaller the hook. A size 28 hook is tiny, while a size 8 hook is substantially larger.
Dry flies are unique in that they’re the only kind of trout flies that are designed to float on the surface of the water. A traditional dry fly is intended to represent the adult stage of an insect. It’s tied onto a light-wire hook and uses its hackle barbs and its tail to support itself on the water. You can greatly improve a dry fly’s ability to float by treating it with fly floatant.
A traditional wet fly replicates an adult insect that has either drowned or is diving down to the bottom of a stream or lake to deposit a load of eggs.
Some wet flies, particularly soft-hackle wets, also do a good job of imitating “emergers” – immature insects that are leaving the bottom and swimming to the surface to hatch out into adults.
Most nymph flies are tied to represent insects in their various immature, underwater stages of development – namely the nymphal, larval and pupal stages, depending on the species of insect. A handful of nymph flies are tied to represent crustaceans such as freshwater snails and shrimp. Keep in mind that trout do most of their feeding – maybe as much as 90% – below the surface. This is why nymph flies work so well!
Streamers are larger flies designed to replicate baitfish, leeches, pollywogs and other “meaty” aquatic life forms. Streamers are especially effective on hefty trout. To them, insects are more like potato chips – a nice snack, but not the whole meal. Streamers appeal to a big trout’s sizeble appetite.