Mayfly Spinner Falls
Frustrated by the mysterious evening rise of trout when nothing seems to be on the water? It’s often a simple case of “Spinner Falls.”
How many of you have fished spinner patterns at least once over the past year? I often ask this question when I’m teaching fly-fishing classes, and I’m no longer surprised when only about ten percent of the anglers raise their hands. This either means there are very few instances when spinners are important, or anglers don’t realize how important they really are. From my experience it is the latter. It seems spinners frequently go unnoticed by anglers even when fish are actively feeding on them. Why? In many cases I think anglers simply fail to recognize when they are available, what they look like on the water, and how fish behave when they feed on them. Once you understand basic spinner behavior, you might find those spinner patterns hiding in your fly box much more important than you once thought.
But first, what the heck are spinners and why are they important? The term “spinner” is the common name for the fourth and final stage in the mayfly’s (Order: Ephemeroptera) life cycle: egg, nymph, dun and spinner. They’re important because they frequently land on the water in great numbers, and trout can’t resist them when they do. More technically entomologists refer to spinners as imagoes, which is just a fancy way of saying they are reproductive adults. This is significant if you are a mayfly because the preceding winged stage - the dun – look very much like spinners, but are not yet able to mate and lay eggs. Entomologists call duns, sub-imagoes, which literally means the sub or pre-adult stage. Thus mayflies have two distinct winged stages – the dun and the spinner. One can easily see the dun stage as they emerge on the water’s surface during a mayfly hatch. Those duns not eaten as they drift on the surface waiting for their wings to stiffen, fly off the water and land on nearby vegetation. There they sit quietly until they molt, or shed their exoskeleton, one last time to become spinners (such as the Green Drake mayfly in the picture above). The length of time before the dun molts varies from a few minutes to a few days depending on the species. Twelve to 24 hours is typical for many species.
Mayflies are the only living group of insects, of the million or so known species, that have two different winged stages. This is one reason mayflies are thought to represent one of the most primitive insect groups still surviving. Some fossil records indicate early representatives of mayflies occurred at least 250 million years ago, making them one of the earliest known insects still alive today. Two other characteristics of mayflies point to their early beginnings. First, they can’t fold their wings flat on top of their back. A handy feature that all other insects, except dragonflies and damselflies, seem to have mastered. Instead, the wings of mayflies either stand straight up or straight out. Second, duns and spinners have no mouthparts and are thus unable to eat or drink. This is another primitive trait, and also explains why they don’t live long. As mentioned earlier the dun stage lasts a few minutes to a few days, and the spinner stage lives a similar length of time. Thus, the dun and spinner stages combined may be as brief as an hour or two and no longer than four or five days. In a nutshell the spinner’s sole purpose is to mate and lay eggs, and they don’t have any time to waste.
And mate they do, sometimes in rather dramatic fashion. Typical mating behavior begins when male spinners form large swarms. The swarms usually develop over water anywhere from a few feet to over 100 feet high. In some cases the swarms occur over land hundreds of meters from any nearby water. Males within the swarm fly with an erratic up and down dance-like motion. At times the whole swarm of thousands of mayflies seems to rise and fall with a rhythmic pulse. Females fly into the swarm, where males rush to be the first to grab a female in flight to mate. Copulation only takes a few seconds, after which females begin laying eggs one of three ways. Most species glide down to the water’s surface one to several times, and release a cluster of eggs each time the tip of their abdomen hits the surface. Some other species release their eggs in flight above the water. A few species crawl underwater – generally down the side of submerged rocks – and deposit their eggs directly on the bottom. Each female spinner lays somewhere between 500 and 5,000 eggs depending on the species. When all their eggs have been released, the females die spent on the water with their wings stretched out flat, creating the infamous “spinner fall.”
It’s critical that you learn to recognize duns from spinners, and how to tell when spinner falls are occurring. For some species duns and spinners look very similar, while in other species they are quite distinct. In all species the key difference is in the wings. The wings of duns are semi-transparent with a smokey brown, gray, or yellow tinge to them. The wings of spinners are completely transparent and clear except for the dark colored veins running through them. The wings of some species have dark colored spots in both the duns and spinners. Don’t let these spots confuse you. The rest of the wing will show the characteristic smokey color in the dun and be clear in the spinner. The body colors of spinners also tend to be brighter than the dull colored duns. Finally, male spinners have very large eyes for spotting females that fly into the swarm, and noticeably longer front legs than the middle or hind legs. These long front legs help hold the female during copulation. While sometimes it can be tricky to tell a spinner from a dun, when seen side by side there’s little doubt which is which.
Spinner falls occur at various times of the day depending on the weather and species. In general during cold weather – fall, winter, and spring – spinner falls occur in the late afternoon. During warm weather spinner falls occur at dusk or early in the morning. One way to judge if a spinner fall is likely to occur is by the size of the surface hatch of duns. Anglers are well attuned to spotting duns popping up on the water’s surface. When a couple days of good dun hatches have occurred you should be on the lookout for a heavy spinner fall later in the day or early in the morning. One excellent clue is seeing swallows feeding heavily above the water. This certainly means some type of insect is swarming. Look carefully for the up and down dancing flight of the male spinners. A small pair of binoculars aimed at the swallows will quickly tell you if it’s mayflies, midges, or some other insect the swallows are feasting on, and what the trout will be feasting on next. Binoculars can also be help you see exactly what trout are taking off the surface. When the swarm of spinners is so thick it looks like fog over the water, you know you are in for some serious spinner fishing.
Confusion often begins once the spinners have laid their eggs and lie spent on the water. That’s because spinners, lying dead on the surface with their wings out flat, are virtually impossible to see, especially in the fading light of sunset (use those binoculars). Further, because spinners a dead, fish feed on them with leisurely, very subtle, almost invisible, rises. Therefore, what the angler sees is a few small rises that look like dinky little fish, and no insects flying off the water to indicate a hatch worth fishing. What the angler doesn’t see is the large size of the fish below those dinky little rises, or the spinners floating flush in the surface film. So, just when things get interesting many anglers think it is all over for the day and head home.
Remember, spinners in the air will mean spinners on the water, even if you can’t see them. So, if you see spinner swarms, pay very close attention to the water for softly rising fish, and look for dead spinners caught in small pockets of dead water behind near-shore rocks or debris. If you find some, definitely pick them up so you can get a fix on their size and color and select an appropriate pattern.
Excellent spinner fishing doesn’t always result in excellent fish catching. I have found that trout feeding on spinners can be some of the pickiest and most difficult trout I’ve ever fished for. Part of the reason is that since the spinners are dead they make no movement on the water other than what the current imparts on them. Therefore, un-natural drag on your fly, of even the smallest amount, will tip off trout that something isn’t right. The other problem is that trout can take up feeding lanes in quiet water where the current funnels spinners down to them. The smooth surface makes it easy for fish to spot the natural spinners on the surface, and easy to spot un-natural imitations and the leaders attached to them. Therefore, fine tippets – 5X at a minimum and 6X or 7X is often needed – and perfect drag-free presentations are critical for consistent success during spinner falls. I also find that downstream slack-line presentations generally fool more fish than upstream or up and across presentations when fishing spinners to picky trout. *When fishing mountain streams, often a Parachute Adams fly is all you need.
On the plus side, the patterns used to imitate spinners are simple and easy to tie. A few split tail fibers, a slender body of dubbing or quill to match the color of the natural, and a pair of spent wings of synthetic or natural material is all it takes. Of course the correct size is important. Spinners, like most insects, always look larger than they really are when seen flying in the air, so try to catch a few naturals to get a good match in size and color. The color and size of males and females differ significantly for some species. When that happens match the female rather than the male, since it is predominately females that end up floating on the water’s surface. Despite all the different species of mayflies out there, the most common spinner color by far is a rusty brown. If you keep a selection of rusty spinners from size 12 to 20 in your fly box, you will be well prepared for most spinner falls you might encounter. *We like Organza Spinners when the fish are really picky.
As this season unfolds, watch carefully for dancing clouds of spinners and the quiet subtle rises of spinner feeding trout. You will find no greater dry fly fishing challenge than when the spinners fall.
For in-depth information on the behavior, effective patterns, and fishing tactics for each life stage – including spinners – of all western mayflies, check out Rick’s book (co-authored with Dave Hughes), Western Mayfly Hatches or his video Advanced Tactics for Emergers and Dries now available for download on Vimeo.