Two other mayflies also show up in the spring: the western March brown and the western gray drake. March browns are size 14 or 12. Western gray drakes, which are sizes 12 and 10, are the largest of the three spring mayflies. There are many March brown patterns; A. K. Best’s Western March Brown is a representative example. Imitate the nymph with a common pattern such as a Hare’s-Ear Nymph.
A.K.’s Western Brown Drake
Hook: Tiemco TMC100 or TMC101, size 14 or 12.
Thread: Tan 8/0 (70 denier).
Tail: Brown hackle fibers.
Body: Dark tan turkey biot.
Wings: Tan mallard for dark lemon wood duck flank.
Hackle: Brown and dark grizzly.
The western gray drake is not so well known; this obscurity might be because rather than hatching midstream, the nymphs swim to shore and crawl out to emerge into winged adults. This shoreline hatch renders the new adults, what fly fishers call “duns,” insignificant because few if any are found on the water. Western gray drake nymphs and spinners, however, can be important, and effective patterns are brownish gray nymphs like an A.P. Nymph or any number of spinner patterns that have brownish gray bodies. Not usually found in heavy concentrations, the western March browns and gray drakes occur in many of the same habitats as blue-winged olives.
Caddisflies are also significant in the spring. Some of the heaviest hatches occur early in the season. The Mother’s Day caddis may be the best known. Near my home in Colorado, these insects usually become active sometime in April, and heavy hatches will continue for several weeks. Peak activity gradually moves upstream over time, so it’s important to find a local source of information to help you pinpoint the epicenter of the hatch.
Mother’s Day caddis larvae are insect green or cream, and they build cases that are square in cross section. The larvae range in sizes 18 to 12. The Peeking Caddis and other cased-caddis patterns mimic the larvae. A soft-hackle wet fly or LaFontaine Sparkle Pupa are good choices for matching the emerging pupae. Productive adult imitations include the Elk-Hair Caddis and ARF Trailing Bubble Harey Caddis.
The green rockworm and the spotted sedge are other early-season caddisflies. Green rockworms range from sizes 16 to 12, while the spotted sedge does not get quite so large—size 16 or 14. The larvae are net builders and they do not build cases, so similar patterns will match both insects. All three early-season caddisflies prefer cobblestone bottoms with well-oxygenated water.
Hook: Tiemco TMC3769, sizes 8 to 2.
Thread: Black 8/0 (70 denier).
Case: Mixed colors of dry fly hackle wound dense and trimmed into a tapered rectangular shape.
Head: Insect green rabbit dubbing.
Green rockworms get their name from their bright green coloration, but they also come in shades of tan. The spotted sedge is generally bright green with a dull olive back. Pupa patterns used for the Mother’s Day Caddis are also good representations of both insects. With respect to the adult insects, select an olive, green, or brown pattern to match the green rockworm, and cinnamon for the spotted sedge.
Stoneflies and More
Stoneflies may be the toughest aquatic spring hatch to match. Most stoneflies mature later in the year. The salmonfly is the first to appear, and it is worth the effort to imitate. The salmonfly can be 2 inches long, and the trout fatten up quickly on this banquet. Adult salmonflies are poor fliers and frequently fall or are blown from bankside brush into the water. Spring is a great time to pound the banks with large dry flies. The trick is that the hatch often corresponds with spring runoff when many streams are difficult or even dangerous to wade. If you cannot hit the dry flies, don’t discount nymphs. Many stonefly nymphs live more than a single year before maturing and leaving the stream, so they are available to the fish throughout the seasons. Dead-drifting tan, yellow, brown, olive, and black stonefly patterns from size 18 to 4 will imitate many different species of stoneflies that might not be hatching but are still a tasty bite. When looking for stoneflies, keep in mind they prefer rubble bottoms and require highly oxygenated, clean water.
Insects are not the only food available to spring trout; baitfish, leeches, crayfish, scuds and cress bugs that spend their entire lives in the water are primary food sources while many insects have not yet awakened from their winter naps. Baitfish, crayfish, and leeches are found in any water that holds trout. Early in the spring, baitfish and crayfish from the previous year will be relatively large. Later, freshly hatched broods will be common but will also be much smaller.
Hook: Tiemco TMC5263, sizes 12 to 6.
Thread: Black 6/0 (140 denier).
Tail: Black marabou with fuchsia Flashabou along each side.
Body: Bloody black Leech Trilobal Dubbing applied in a dubbing loop.
Hackle: Whiting coq de Leon hen saddle.
Include a few eggs patterns in your fly box. Spawning fish introduce this nutritious food source to the stream, and the trout quickly feed on drifting eggs.
Leeches may be as small as a half inch or up to several inches long. Colors vary widely, including black, brown, tan, olive, yellow, and maroon. Scuds and cress bugs require significant weed growth, and the best populations occur in still waters, spring creeks, and tailwaters, but don’t be surprised to find them in stretches of freestone waters if weed growth is present.
With all these water types and the smorgasbord of foods available in the spring, be sure to plan several trips to this corner of the country. You’ll need plenty of time to explore the vast range of fishing experiences and opportunities.
Al Ritt is one of Colorado’s premier pattern designers and fly tying instructors. He is also an innovative fly tying tool designer, and played a key role in creating the terrific Peak fly tying vise.