Family: Simuliidae (Blackflies)
When one thinks of flies, this is the one that typically comes to mind, but many anglers are unaware of their success before they reach the annoying adult stage we know so well.
The Blackfly (Simulium vittatum) is a common food source for trout, especially during the underwater larval stage. Their larvae are worm-like and attach themselves to rocks. They are particularly active during the late summer and early fall on tailwater fisheries in Montana.
Savvy, Montana fishing guides know to watch for these insects when fishing is slow on standard patterns as trout key into the pupae, becoming highly selective for a few hours in the mornings. Identifying blackflies can be challenging as they don's stay on the water very long as adults. The best fly fishing tactics to try when trout are being highly selective to these pupae is to use a dry dropper rig with a zebra midge about 3' below the dry fly.
These often unseen insects are very important to trout on the lower Madison River during the early morning hours.
The rear portion of the larvae can be twice the thickness of the head, so ensure the profile of the fly is accurate for the most success when fishing these flies. They are often found in fast-moving, highly oxygenated sections of rivers, so focus your efforts there.
Blackflies rocket to the surface when ready to hatch, so trout will eat those as well.
They can range from gray, yellow, olive, brown, cream, and black.
3 Montana Rivers Where Trout Key Into Blackflies
3 Essential Blackfly Imitations For Fly Fishing in Montana
