Parks' Fly Shop: Guide to Yellowstone Area Other Aquatic Insect Hatches, Yellowstone Hatch Chart

Guide to Other Aquatic Insects in the Yellowstone Area

The following table and discussion include information on midges, damselflies, and other aquatic insects besides the "big three" that can be important when fishing Yellowstone country, especially in the offseason or on specialized fisheries such as lakes.

One nice thing about the Yellowstone area is that midges are usually not all that important, especially in the summer. The major exceptions are the tailwaters and spring creeks, and a few situations here and there, which are discussed below.

Other Aquatic Insects Emergence Table

Table Key: X=primary importance, x=secondary importance, blank=unimportant
Name Description Active Time Month
      Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Midges, Various Most size 18-22. Colors discussed below. Varies. AM in the summer, afternoon in the winter. X X X X x x x x x X X X
Midge, Large Black Large black early summer midge. #14. Midmorning until early evening.           X X          
Midge, Late Summer/Early Fall #18-20, very dark olive to black with almost clear wings Morning.               x X      
Chironomids #8-12, various colors. Like large midge larvae/pupae All day       x X X x x X x    
Craneflies Generally tan, cream, or brown, like a daddy long-legs or very large midge. Morning usually.           x X X        
Damselflies Our local damsels tend to be red-brown or blue as adults. The nymphs are olive green. #10-14. Late morning through late afternoon.           x X x x      
Dragonflies Red or green. Late morning through late afternoon.           x X x        
Water Boatmen and Backswimmers Black or olive, long legs During the day in lakes and backwaters         x X x x X x    

Discussion of Insects

Boldface type indicates fly patterns. Italics are used for scientific names.

Midge, Various

As noted above, midges are not quite so critical in our immediate area as they are in many others, mostly because we don't have many tailwaters. Midges are most important in our area on the spring creeks, in lakes (mostly Chironomids, discussed in their own entry), in the winter, and in a few scattered emergences at certain points in the season.

For adult midges, with the exceptions given below, you should carry Griffith's Gnats and black and cream Jewell Midges in sizes 18-22. An olive and gray midge would also be a good choice. For larvae, carry String Things in cream, tan, olive, black, brown, and especially red. Realistically, you only need to carry these in the winter or on the spring creeks when no prominent hatches are expected. For pupae, carry Red Haze Serendipities, Black and Copper Zebra Midges, and various iterations of "thin body, prominent rib, large head" midges, such as Brassies, Jujubee Midges, Disco Midges, etc. There's a huge range of these flies, all of which are very similar in terms of overall "look." Carry several colors. These can be important even in the summer on rivers where otherwise you'd expect to match mayfly/caddis/stonefly hatches or just to fish attractors. WD-40s are a great midge/BWO crossover nymph. Carry them in olive dun with a gray thorax.

Midge, Large Black

This one is worth noting because it's big (#14) and can draw selective rises. The old-school Black Gnat is a great match for this, as is a Black Caddis or dark-winged Coachman Trude. Look for this insect on the Gibbon in mid-late June and the Yellowstone in mid-late July. The larvae and pupae are unlikely to matter on these rivers.

Midge, Late Summer/Early Fall

Late August and early September frequently bring morning midge emergences in the Lamar drainages. The trout are otherwise quite lethargic at this time, especially when the nights have been cold, so matching this insect is important. Look for trout rising to it in the lower halves of pools, often in very shallow water. Rises will be very casual and slow. The best dry is a #20 black Jewell Midge. The best pupa, which can work either dredged deep or as a dropper, is a #18-20 black Zebra Midge with a copper wire rib. Other shops also sell patterns designed to match this insect, and I imagine they'd work too.

Chironomids (aka Big Lake Midges)

Chironomids are just big lake midges. In our area, they are especially important as larvae and pupae in private lakes. The best basic pattern is the "snowcone" style, with a 2-3xl #10-12 hook, white or silver bead, and either black or red body with a silver, white, or red rib. Large "buzzer-type" flies are also good choices. Good colors are red, black, light brown, light olive, and purple.


Cranefly larvae are starting to get some traction in the area, but we seldom use them. Once in awhile you'll see an ungainly large midge-like bug skating across the surface and get inhaled, but unlike some other rivers in Montana it doesn't seem like our area's streams have selective rises to this insect.


Damselflies are primarily important on small public lakes in YNP and in some of the private lakes, though the slower stretches of the Firehole also see an occasional hatch. As adults, most of our damsels are the standard blue or reddish-brown (almost cinnamon) and about a size-12 through the thorax, though imitations should have long abdomens. For nymphs we like drab, impressionistic flies, such as Minch's Skinny Damsel.


Legend Charlie Brooks stated that dragonfly nymphs were critical on some area rivers, but odds are the fish were taking them as something else. We've never seen fishable numbers of dragonflies, though there's always a few buzzing around.

Backswimmers and Water Boatmen

Contrary to popular belief, these insects do actually "hatch" from time to time, but they are far more important in their aquatic stages. Peacock-bodied nymphs are good general imitations of these bugs, and should usually be fished as droppers behind streamers. Most important on the private Paradise Valley lakes, though not REALLY important anywhere.

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