Fly Fisherman Throwback: A Primer of Stream Entomology-II

Editor's note: Flyfisherman.com will periodically be posting articles written and published before the Internet, from the Fly Fisherman magazine print archives. The wit and wisdom from legendary fly-fishing writers like Ernest Schwiebert, Gary LaFontaine, Lefty Kreh, Robert Traver, Dave Whitlock, Al Caucci & Bob Nastasi, Vince Marinaro, Doug Swisher & Carl Richards, Nick Lyons, and many more deserve a second life. These articles are reprinted here exactly as published in their day and may contain information, philosophies, or language that reveals a different time and age. This should be used for historical purposes only.

This article originally appeared in the May-June 1972 issue of Fly Fisherman magazine. Click here for a PDF of the print version of "A Primer of Stream Entomology-II."

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Part Two of a series of articles designed to familiarize fly fisherman with the practical aspects of stream­ side entomology. The series will cover the favorite fare of trout, smallmouth bass and even bluegill in all of their habitats, slow water and fast, from farm ponds to high mountain lakes. Mr. La Fontaine is both a scientist and fly fisherman who goes where the fish and the hatches are.

Change is good for a trout fisherman, and the leaving of familiar streams and familiar problems will force him to think fresh and learn anew; even if he will not catch as many fish on unfamiliar streams, even if leaving means leaving the gem streams of Montana just before the golden autumn.

Through the late summer and early fall I fished across the northern trout belt of the country. In mid-September my wife and I settled in Connecticut for a temporary stay and I began to scout the state for a trout stream to adopt. I did not expect to find the Madison or the Missouri, and I didn't, but I found a clear, bouncing stream, the Jeremy's River, and that was fine.

I was fishing upstream towards the road and the angling was steady for 10- to- 12-inch browns, but I thought that it could be better. I changed from a #18 Blue Wing Olive dry to a #16 Baetis nymph. At a large pool in front of the road bridge I saw the tiny bubbles of a fish sipping from the surface film. I cast four times to the fish with the nymph, but he stopped rising after the last cast.

While l rested the fish, which I thought to be a decent trout because of the preferred position in the feeding lane. I remembered autumn days of large trout on the Madison or the Missouri or the Clark's Fork; fish that might not have bothered with small hatches of mayflies, but that fed on the tiny pupae of the Chironomidae (Tendipidae) midge and struck at my Midge Pupa imitation.

I did not raise the fish that evening. I seined the water before I left, because the feed might be leaf-hoppers (Jassid), or minute ants, or bark beetles, but an Olive Chironomidae pupa was dominant in the sampling. Two days later I caught the fish, a 17-inch brown, by casting a #22 Olive Midge Pupae amidst the white foam specks and leaf bits of the pool's eddy. There were Chironomidae midge in the mouth and gills of the fish. I released the brown, my only Connecticut trout of over 13-inches of the autumn. Well, I thought, food is food and fish are fish, and some things are the same whether in Montana or Connecticut.

I think that no matter where a trout stream is located, or whether it is a chalk stream, a meadow brook, or a large river, midge pupae are important at some time of the year in the diet of the fish. The cause of selectivity in a trout, and the reason for a trout feeding consistently on any item, is a simple equation:

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abundance of food item X bulk of food item / difficulty of capture = energy spent per calorie consumed

Midge pupae rate high in availability. Chironomidae go through a complete life cycle: egg, larva, pupa, and adult; and while the larval and adult stages are fed upon by trout, it is the pupal stage that attains primary importance during certain seasons. Although the bulk of a midge pupa is small, the insect rates high in abundance and availability, making the energy value high enough to let trout of over five pounds feed on them.

When pupation of one of the year's multi-generations begins, the family of Chironomidae employ the survival device of overwhelming the predator. Large numbers of the insects drift, hanging at or just below the surface film. Because in late summer and early fall a constant hatch of larger insects might be absent, a trout will feed on the midge pupae, which float helplessly. The trout need not expend a lot of energy chasing, or even rising to, the insect as it must to a mayfly. In a quiet eddy or drift lane, where the directionless pupae will gather, the trout can hang just below the surface and sip great quantities of food at leisure.

For the angler stalking the smutting trout there are three considerations: water choice, method, and tackle. The primary feeding lanes are the drift collecting areas, eddies, slow down channels, and pool edges, because the trout need not work to hold position in the current and he can feed on slowly drifting pupae. Naturally, lane areas near deep water and cover are the best for large trout.

The tackle fits the method. A small rod handling a #4 line is more than an affectation. The #18-20-22 fly must drift like the natural, just below the surface, without drag. With a small line and a 6X or 7X leader there is a soft delicacy; even more important than the low visibility of the leader is the pliability of the fine, limp tippet which allows free movement of the fly.

The method of fishing is a greased line technique. The line and leader, up to the last 18 inches, are treated with floatant. The casts are upstream and the line is mended, as in dry fly fishing, enabling the fly to float free. As long as the tip sinks I do not believe that the floating leader disturbs the fish, and the mending of a high-floating leader does not cause the sunken fly to move as much as in the case of a deep leader. Strikes are indicated by the dip of the floating part of the leader.

I tie the midge pupae patterns on dry fly hooks with upturned eyes. Although the flies are fished wet, they are buoyant and they stay near the surface. The thorax is made of fur, the abdomen of quill or stripped herl, the tail tuft of soft hen hackle, and the collar of cock hackle.

Midge Pupae Patterns

• OLIVE: thorax: olive; abdomen: stripped peacock herl; tail tuft: black; collar hackle: black.
• BLACK: thorax: black rabbit; abdomen: stripped peacock herl; tail tuft: black; collar hackle: black.
• CLARET: thorax: claret rabbit; abdomen: quill, dyed red; tail tuft: brown; collar hackle: brown.
• CREAM: thorax: cream rabbit; abdomen: light ginger quill; tail tuft: cream; collar hackle: medium ginger.

If next fall I'm not on the Clark's Fork or the Madison, I'll remember that nearly any stream carries a float of midge pupae, and then I'll fish for the big trout that feed on those tiny pupae.