The Little Lehigh Fly Shop was on the banks of a fine limestone spring creek. I spent many years observing the stream, just about 24/7. 365 days a year.
I couldn’t understand, AND STILL DON’T, why the freestone fisherman abandoned salmonids or flew to cooler locations when the weather got hot. The Little Lehigh was entering its prime time of the year, Tricos in the morning. hex’s in the evening and always, always MIDGES!
Midges hatch all year long and usually emerge during the nicest part of the day, they experience a complete metamorphosis egg, larva, pupa and adult. Two, three or more generations occur per year.
The life cycle takes from 2 to 4 weeks or as long as a year.
The farther north you go the larger they get.
Dr Ernest Schwiebert told me the most important thing about the presence of adult midges on the surface film is that there are pupa under the film. Most anglers agree the pupal stage is most important to the angler.
Suspect midge pupae whenever trout are rising but you can't see what they are taking
My favorite pupal imitation is..
Pupa float to the surface slowly, bodies moving feeblely in a swimming motion.
When they reach the meniscus (surface film) they
hang vertically in the film, struggle out of the pupal hus and fly away.
Trout sip them in, leaving only a tiny dimple at the surface.(dimpling rise)
Imitate this activity by-dressing your leader to within 6" of the fly to present your imitation just below the surface film.
More About Midge Pupae
Midge eggs develop into larva. Larvae are wormlike aquatic versions of the insect.
Prior to emergence, larvae seal themselves inside of an immobile pupal chamber and transform to a pupa.(Dr. Ernest Schwiebert told me the most important thing the presence of midge adults tells you is that there are pupa in the film.)
Prior to emergence the pupa congregate in the slow water, or “cushion” at the bottom of the stream. (Wild Trout also concentrate there because fish can't spend their llives fighting the current). As the concentration of pupae increase, the trout notice them and begin to feed on them.
When it's time for the pupa to "hatch" they ascend from the cushion, to the surface. The trout follow them to the surface and suspend.
Upon reaching the surface the pupa encounter the surface film (meniscus.) This is a big deal because it's difficult for the pupa to penetrate the film..Midge pupa suspend below the meniscus and bore a hole through which they crawl to ride the surface, Surface tension holds the pupal shuck under the film. Trout pick off the vulnerable emerging pupa as they struggle to penetrate the film.
The most effective midge pupa imitation I know of is Al's Rat.
The Rat can be sight fished to a visible fish. Dress your 8x tippet to about ten inches from the fly. Fish it dead drift just below the film. Al Miller (father of the Rat) sometimes twitched it. When the fish were lying on the bottom he added a shot and fished the cushion.
Some folks sight fish with the Rat some fish it blind, some across and downstream.
I believe the “primary trigger” is the silhouette provided by the dark brown monochord.
The "rat" works all day, all year. For many it's the first fly they try every day all year.
The "Rat" can be particularly useful during periods of "Behavioral Drift." Gary Borger’s book "Presentation" provides an excellent description of this phenomenon. Try the "Rat" at dawn and dusk when large numbers of midge pupa are in the drift.
Al's Rat is always in my fly box. Of all the flies I sold at my shop, the Rat outsold all of them.
After adults penetrate the surface film. I imitate the adult with the Griffiths Gnat, The brain child of George A. Griffith.
Mr Griffiths tied the fly on a size 20 hook with a peacock body palmered with grizzly hackle.
He introduced the fly to Dr Ernest Schwiebert who popularized the fly in his classic book “Nymphs.”
Schweirbert told me the Trout took the Gnat for a cluster of resting or mating diptera on the surface film.
Dr Schwiebert varyied the body material, sometimes substituting muskrat or floss for peacock.
Anytime I can incorporate peacock into a Spring Creek pattern I do, so I sick with the peacock body. I tie it in sizes 18 to 28. The most common size is #18.
Mr Griffiths pattern is my “go to” pattern when adult diptera are on the water.
...a member of the Kapok family, is a great floater. Try it fo dubbing or wings on midge patterns
Attention to size is crucial. During a #28 hatch. a 1-mm variation from the natural means at least a 30% dimensional error.