Alderfly

ADULT SIZE: 10-15 mm (3/8 to 5/8 in)

ADULT COLOR: Black or dark brown

OTHER CHARACTERISTICS: Adults resemble caddisflies, but have no hairs on their wings.

Mouse-over for alternate views: Larva    Adult    Adult dobsonfly

About Alderflies

Your first impression of an adult alderfly may be, "Wow! That's one big black caddis!" Look a little closer, though, and you'll become aware that something is missing: there are no hairs on the wings. And that absence is the only reason this bug is important to fly anglers. You see, it's the hairy wings that make caddis float, and the lack of them makes alderflies imitate the Titanic.

When an alderfly falls onto the water from an overhanging tree, it slowly sinks. And because alderflies are large enough to make a good snack for a hungry trout, they usually don't sink very far before they're eaten. It's a happy coincidence of favorable events: first, alderflies are a spring hatch; second, it's a time of year when the water is high and into the trees; third, trout are especially hungry after a winter menu of midges and blue-winged olives.

So a good spring strategy is to look for overhanging trees (such as alders) either on a lake or a very slow part of a stream. Then cast a large black Soft Hackle into the water below the tree; let the fly make a loud "plop" when it hits the water. And sit there quietly, maybe giving your fly an occasional small twitch. Hang on tight, because strikes can be aggressive! Also, you might want to bump up your tippet size since you'll have to manhandle your fish out from under all those branches.

Alderfly larvae prefer slow water or lakes. They crawl around in plant debris and eat other insects. When ready to pupate, they larvae leave the water; pupation and adult happen out of the water. The adults then hang around in the trees looking for mates. Thus the only stage worth imitating is the adults.

Dobsonflies are similar to alderflies, except they are bigger. They are more common east of the Rockies, where larval imitations can be productive. However, their significance to western fly anglers is very limited.

STAGE

PATTERN

SIZE/
COLOR

PRESENTATION

WHERE

Adult

Soft Hackle

8-12/Black

Count-down-and-retrieve, Chuck-and-sit

Lakes; backwaters and slow sections of rivers