Seated quietly in my pontoon boat, I was elevated, where the setting sun's reflection created a stunning impasto display of pastel hues—Cobalt Violet, Cadmium orange, and Barium Yellows, all coated in a chromatic grey. It was reminiscent of a Monet-style painting, showcasing the unique artistry of Mother Nature. Suddenly, a tiny insect with fluttering wings emerged from the water's surface, slowly ascending as the last shedding water droplet fell back into the lake. I was captivated by the sight of the Corixae, which spread its limbs wide in flight as if suspended on a rising crucifix—a moment of pure beauty. Within a fraction of a time, a rainbow trout surged, nudging the Corixae even higher, narrowly missing it as the Corixae brushed against the trout's snout. Everything was within arm's reach, filling me with wonder and appreciation for the natural world. This private moment during the early fall Green Corn Moon for the fly anglers is characteristic of a double cabriole derrière, and no performance in nature is more satisfying.
This image has remained in my memory for decades because it showcases the importance of the Corixae as a food source for our local trout. It vividly illustrates how eager and frantic the trout becomes while trying to gather this food item. It would make a perfect magazine cover.
As a Western Canadian angler, I feel fortunate that several people recognized the importance of Boatmen and Backswimmers in a trout's diet several decades ago in our region. People like Rick and Shirley Hilburn, Tak Yu, and others were instrumental in local fly development at those times. Worldwide, most fly anglers do not carry these patterns as part of their regular inventory, and many have never heard of Backswimmers or Boatman or fished with them. My friends in the UK, USA, and Europe—who extensively fish still waters, lochs, or lakes—rarely consider these insects significant. This may be the case in these regions if the migration density is not high volume.
Backswimmers and water boatmen belong to the family Corixidae. They inhabit similar aquatic environments, move in comparable ways, and are both accepted food sources for trout. Trout doesn’t differentiate between the two types of insects, and neither should anglers. The presentation and tying of these patterns are very similar, allowing anglers to fish them in the same manner without needing to be familiar with every species. Focus on tying simple, practical patterns and fishing them using the same tactical approaches. One important thing for the angler is whether the fish are taking the Corixae at the surface, on the pause, or while diving. This will determine whether your retrieve or lack thereof suits the fish’s behaviour and needs.
I have reignited my interest in Boatman patterns in recent years, mainly because we have used the same two patterns and tactics for the last three decades—it's time for a change. There are specific times of the year when they are highly effective. During the spring Corixae mating season, around the time of the Milk Moon, shortly after the ice thaws on lakes, and again in the fall—from the Green Corn Moon to the Harvest Moon and the first frosts of the season—Corixae patterns become significantly crucial. The activity of corixae is extensive, and if it were a hatching cycle rather than a migration cycle, fly anglers would find it significant.
During the Green Corn Moon, they leave smaller bodies of water that cannot sustain them through the winter months. This migration can be observed as tiny water droplets hitting the surface, a key indicator for selecting flies that mimic these insects. If the activity is extensive, you likely will find a few lying at the bottom of your boat.
After searching the web for innovative patterns for backswimmers and boatmen, I quickly realized there was a limited selection available in floating and sinking designs that were genuinely distinctive and had the right physical properties to work effectively. Many flies would work, but they often had distractions due to their construction. Either they weren't balanced correctly, placed too much emphasis on parts that trout wouldn't see, or that wouldn't matter to them, had incorrect profiles, or looked messy with little regard for tying techniques, balance, or proportions. If form follows function, then the patterns of Corixae should be designed to float or sink, and both require space in your fly box.
After the first frosts, we often see a migration of Backswimmers and Boatman. At this time, they leave smaller bodies of water that cannot sustain them through the winter months. This migration can be observed as tiny water droplets hitting the surface, a key indicator for selecting flies that mimic these insects.
I wanted more than just a fly that would catch some fish; I was looking for a genuinely effective pattern that would be irresistible to the trout and long-lasting. A couple of years ago, I began working on this pattern, incorporating some of the traditional philosophies associated with this style. Blending the old with the new seemed logical. Traditional patterns often featured flashy materials at the rear to mimic the air bubble, which helps fish recognize these forms as prey.
Another key aspect of traditional designs is that backswimmers and boatmen, when at rest, maintain a suspended position with their heads down and rear legs pointing forward at approximately 45 to 60 degrees relative to their bodies. As a result, we developed a series of boatman and backswimmer patterns in various colours. These were designed as attractor patterns evident in stained or murky water. They also function well as lures in clear water, enhancing visibility to draw fish to your set of flies.
With a selection of natural-coloured patterns featuring both floating and sinking characteristics, we found this approach to be a better choice when fish explicitly targeted these insects.
In the late eighties, while on one of our local lakes, we encountered a migration of Boatmen. The day was characterized by a light breeze across the water and clear skies. We observed countless large trout gorging themselves to the point of regurgitation, feeding primarily on Boatmen. With the slight breeze, we drifted with a drogue attached to slow our movement across the lake, casting floating lines toward rising fish. The downwind cast allowed me to effortlessly land 30-50 feet of fly line, plus a twenty-foot leader with a team of Boatman patterns and a bright orange Gurgler on the point.
Interestingly, this was the first time we had ever spotted predominantly white/off-white boatmen that shimmered with bright green/chartreuse along all the leading edges of their shells, legs, and thoraxes with a distinct black/brown patch on the top of the thorax section behind its head. From a distance, when they hit the water after taking flight, they resembled scattered white popcorn on the floor of a movie theatre before tucking their wings beneath their shells. They were everywhere, and trout of all sizes eagerly devoured them. This adolescent behaviour was reckless at best, but it yielded great results for anglers.
Chartreuse was a new colour in the fly-tying industry at the time. Few people realized it could be a highly effective trout-attracting colour under light, water, and wind conditions. Over time, this colour became a favourite among fly anglers targeting Northern Pike, Walleye, and Bass.
The fly pattern derived from this colour variation of the Greater Water Boatman (Notonecta undulata) was a well-kept secret for many years. If you told fly anglers at the time that you were using a white and chartreuse boatman, they would laugh at you. I was OK with this and eventually stopped sharing the pattern because most people weren't even fishing with it. As a result, the Greater Water Boatman fly pattern became my secret weapon during the late season. Today, we call it the Cat Whisker Boatman only to identify the colour scheme on the profile.
Water boatmen and Backswimmers are aquatic bugs with oar-like hind legs that paddle along the water surface or dive to feed in moderate water depths. While Backswimmers do not often congregate, it is common among Water boatmen. They occur in fresh or brackish water worldwide and may be abundant in certain ponds or lakes. About 525 species are known worldwide, 132 in North America. There are both migrating and non-migrating species.
The main attraction for anglers is that fish and corixae are willing to move freely and boldly in calmer waters, such as early spring and late fall. As both species move and cover larger water areas, the likelihood of encountering each other is inevitable. Simple patterns are often the most effective. Paying attention to hook size is essential, as smaller hooks offer less space to work with. Adding too many components can make it challenging to tie small patterns, especially if you want to include legs, flash, and body materials.
A more straightforward approach generally works better, such as a fuller-dressed spider style or tail-less wet flies that focus on colour and hackle movement. Larger patterns, ranging from size eight to twelve, can accommodate more materials due to their longer shanks, allowing for the addition of legs and more significant amounts of flash to attract fish.
What specific techniques can be used to tie effective Boatman and Backswimmer patterns?
One key point when tying the Corixae patterns is the length of the body-to-leg ratio.
- The legs are set at a 45-degree angle facing forward and should be hook shank length.
- They breathe air and carry an air bubble while diving to breathe - this often has a silvery or pearlescent colour.
- They will adopt the colouration of the bottom substrate or predominant vegetation. Matching the lake bottom colour is an old method that has value in its belief in being effective. Shades of green, tan, olives and brown are appropriate.
- The roundness of Corixae calls for a stout pattern tied on standard or 1XL hooks on 1X or 2X strong hook gauge. Sizes 8-16
- Some tiers add lead to the pattern. I choose not to and allow the hook weight to be 1x or 2 X gauge hooks to be the weight. A slower descent is much more controllable in lake fishing scenarios.
- Floating backswimmer patterns are made of spun deer hair, closed cell foam or are suspended with a foam arse end.
Are there particular environmental conditions that make the migration of these insects more pronounced?
Insects undertaking seasonal migrations serve as vital ecosystem linkages by subsidizing food webs. Such transfers of insects imply that even food webs that seem isolated may be closely connected. One such linkage that has largely gone unstudied is the seasonal migration of corixids, which fly from geographically isolated wetlands into large lakes and rivers every fall to overwinter. For the fly angler, this is very predictable from year to year. Much further documentation of the phenomenon of corixid migration in North America is needed while also investigating the ecological importance and drivers of this movement across the landscape.
Corixae migrations can lead to drastically increased food densities within standing or slow-moving water areas. Corixids enter every meter of water immediately adjacent to the shorelines of lakes, where landings are concentrated and in open water on lakes during high wind days. The stomach contents of trout in lakes heavily utilize this forage, with corixids present in 97% to 100% of these fish and accounting for 38% to 97% of stomach contents by weight during the corixid migration period in fall.
This could have implications for the productivity and overwintering survival of corixid-feeding trout. A lot of food can enter a trout lake just before our northern lakes freeze. The overwintering strategy of corixids that do not migrate to rivers and lakes in the fall is poorly documented. Little is understood about the ability of these insects to survive in wetlands that freeze solidly—multiple corixid species in wetlands at ice-over, with only some species reviving after thawing. During our winters, most corixids group together within air pockets, often observed while ice fishing and cutting holes in the ice. The study of corixids overwintering in ice represents a little-understood survival mechanism of aquatic invertebrates in shallow wetlands, the understanding of which could help predict how the abundance of these organisms might change in the face of altered overwintering conditions. The seasonal flights of corixids between wetlands and larger water bodies may represent one of the world’s great insect migrations, which has largely gone unnoticed but could have important implications for ecosystem functioning and conservation in the North American prairies.
What are the most successful fly-fishing strategies targeting trout during peak Corn Moon and Harvest Moon periods?
Patterns should be presented to mimic the corixae's oar-like swimming motion. The most straightforward technique is to make a cast, allow the fly to sink for a few seconds, and then initiate a pulsing retrieve. Some anglers achieve this by twitching the rod tip, while others retrieve the line with short, jerky pulls of 1 to 3 inches on a floating line with a 12-foot leader and a single fly pattern. This approach is popular among one-fly anglers and provides an excellent way to start fishing with backswimmer patterns, particularly if you're struggling with casting or are new to fly fishing.
My preferred method is to fish with a floating line and a large floating-point fly to keep the back end of the leader at the surface. I attach two dropper tags, five feet apart, to a twenty-foot leader. After casting, I pull the fly line and leader straight, then pause to allow the front two flies to sink to a depth of up to four feet.
At this stage, I begin making short, jerky pulls on the line, incorporating frequent stops during the retrieve. Fish often hit the fly during the pauses as they suspend and sink slowly. After a pause, the flies ascend in the water column when I start pulling with the short, jerky retrieves. Then, during the next pause, they slowly sink again.
This repetitive motion of several short pulls, moving the flies 1 to 3 feet or more, raises the patterns higher, bringing them closer to the surface. The pause allows the patterns to sink to a depth of 1 to 4 feet. This technique mimics the movement of corixae exceptionally well.