Fly Fisherman Throwback: West Yellowstone's Major Insect Hatches

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, John Voelker, 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 July 1983 issue of Fly Fisherman magazine. Click here for a PDF of the print version of "West Yellowstone's Major Insect Hatches."

---

The West Yellowstone area has become a mecca for fly fishermen because it is surrounded by an extraordinary number of trout waters which offer diverse challenges to the angler.

During May and most of June, heavily weighted imitations of stonefly nymphs, caddis larvae and sculpins fool some very fine trout. But above all, the area is renowned for its hatches of aquatic insects. The very best of these take place from late-June to about mid-September. Much has been written about autumn as the season to pursue big browns with streamers and nymphs. This is true, but superb dry fly fishing continues through October, although the options are more limited than during the summer months.

The three-week period from June 20 to July 10 attracts more fishermen any other time of the season. It's debatable whether this period produces the season's best fishing, but these anglers are dry fly enthusiasts who know that each year at this time they will find the hatches of Western Green Drakes on the Henrys Fork and giant stoneflies or "salmon flies" on the Madison. The hatches of these two insects certainly bring more large trout to feed on the sur­ face than any others.

It is no secret that on most of the better rivers and lakes the best fishing begins as the salmon fly hatch on the Madison winds down. Outstanding caddis hatches on the catch­and-release areas of the Madison and Yellowstone produce some of the best dry-fly fishing anywhere. Hebgen Lake has to rank as one of the world's best stillwater dry-fly fisheries, with August being the prime month.

As the caddis and mayfly hatches taper off in August, terrestrial insects become an important food source for trout. Grasshoppers are the main attraction. When trout are feeding on hoppers the action can be fast and furious. August through mid-September is the best time to fish terrestrial imitations on all the streams in the area.

Montana's Big Horn River has been re-opened to fishing for one full season and part of another. It has the characteristics of a spring creek except for one: a consistent flow. During much of the prime dry fly season in 1982 the Big Horn flowed at levels which sometimes doubled those of 1981!

This makes predicting hatches a risky venture. The Big Horn has the heaviest mayfly hatches I have ever seen, mostly Baetis, Ephemerella and Tricorythodes. In 1982 the best hatches occurred in May, August, September and October. Clouds of caddis were a welcome annoyance from mid-August through September. Their presence created some spectacular fishing, especially during the first half of September.

The following chart lists major hatches of aquatic insects as they occur during the season. These insects and others hatch on other streams and lakes in the area, but not as predictably or abundantly as on the waters listed.

Major Hatches

STONEFLY–“Salmon Fly”–(Pteronarcys californica)

• Henry's Fork May 22 through June 15
• Big Hole June 14 through June 25
• Madison June 25 through July 10
• Yellowstone July 10 through July 25
• Gallatin July 10 through July 25

Size–#4, #6, #8

---

CADDIS–many species–(Trichoptera)

• Henry's Fork June 5 through July 15
• Madison July 1 through August 15
• Firehole June 5 through July 15
• Yellowstone (Y.N.P.) July 15 through August 15
• Gallatin July 10 through August 15
• Bighorn August 10 through September 30

Size–#12, #14, #16, #18

---

MAYFLIES

Pale Morning Dun–(Ephemerella inermis & Ephemerella inftequens)

• Firehole June 10 through June 30
• Madison (Y.N.P.) June 15 through July 5
• Henry's Fork June 10 through June 30 & July 15 through August 31
• Bighorn August 1 through September 1

Size–#16, #18, #20

---

Western Green Drake–(Ephemerella grandis)

• Henry's Fork June 21 through July 1
• Madison (Y.N.P.) June 15 through June 30

Size–#10, #12

---

Brown Drake–(Ephemera simulans)

• Henry's Fork June 25 through July 5
• Gibbon July 1 through July 10

Size–#8, #10

---

Small Western Green Drake–(Ephemerella flavilinea)

• Henry's Fork July 5 through July 25
• Madison (C&R) July 20 through August 10

Size–#14, #16

---

Tiny Western Olive–(Pseudocloeon edmundsi)

• Henry's Fork July 15 through September 30
• Firehole September 15 through October 31

Size–#20, #22

---

“Tricos”–(Tricorythodes minutus)

• Hebgen Lake July 15 through September 15
• Madison (Y.N.P.) August 1 through September 30
• Henry's Fork August 1 through September 30
• Bighorn September 1 through October 15

Size–#18, #20, #22

---

Speckled Spinner–(Callibaetis nigritus)

• Hebgen Lake July 15 through September 15
• Centennial Valley Lakes July 15 through September 10

Size–#14, #16

---

Little Western Iron Blue Quill–(Baetzs parvus & Baetis tricaudatus)

• Firehole June 10 through June 30
• Madison (C&R) May 1 through June 1 & September 20 through October 31
• Yellowstone (Y.N.P.) September 20 through October 31
• Bighorn April 15 through May 25 & September 15 through November 30

Size–#18, #20, #22

---

*Y.N.P.–Yellowstone National Park

*C&R–Catch and Release section of the Madison

---

Brad Richey was co-owner of Madison River Outfitters, a fly shop and guide service in West Yellowstone, Mont.

---