Fly Fishing Bugs

In fly fishing bugs are very important to understand if you want to catch fish. Most flies are tied to imitate a specific type of bug or to give a general buggy impression. The closer you can get to what the fish are eating the more likely you are to have success. There are 5 main groups of bugs in Colorado that you need to know about and I will list the common flies that are used to imitate them.



Mayflies (Ephemeroptera) are aquatic insects that have a life span of about one year. The adult of this bug is easy to identify with clear wings folded together on the top of its body and two or three tails protruding out the back. Here are the stages and the names fly fishers identify them by. Names like BWO(blue winged olive), PMD(pale morning dune) and Baetis are all refer to specific mayflies hatches.


Nymph - underwater larva form

Emerger - adult nymph swimming to the surface to hatch

Dun - an nymph molting to an adult on the surface of the water waiting for it's wings to dry

Spinner - sexually mature adult that falls to the water after mating.


Nymph - Pheasant Tail Nymph

Emerger - Barr Emerger

Dun - Sparkle Dun

Adult - Adams Dry Fly



Caddis (Trichoptera) is an aquatic based insect similar to a moth or butterfly. They can be identified by the wings tented over their back and the long antenna. This fly fishing bug starts hatching around Mothers day and is found on the water until the first snow. The nice part about fishing a caddis imitation is that it does not always have to be fished as a dead drift. Caddis bounce off the water surface and trout take them in a splashy rise.


Nymph - underwater larva form

Pupa or Pharate adults - a larva that has pupaed and is heading to the surface to hatch

Adult - fully mature Caddisfly


Nymph - Hare's Ear Nymph

Pupa - La Fontaine Sparkle Pupa

Adult - Elk Hair Caddis



Stoneflies (Plecoptera) tend to be large with a orange band between the neck and thorax. The one in the picture is from the Gunnison River during the June hatch. If you can not handle large bugs crawling on you, I would not recommend fishing this hatch. Stoneflies are very sensitive to water pollution and tend to hatch in the beginning of summer.


Nymph - underwater larva form

Adult - Sexually mature adult


Nymph - Kauffman's Stone

Adult - Chernobyl Ant


Midges (Chironomidae) are the most abundant food source available to trout. Midges undergo a full life cycle and are very similar to mosquitoes in size and shape. They are available year around and most of the flies used to imitate them are small and simple. Fishing a midge pattern will usually produce when all else has failed.


Nymph - underwater larva form

Pupa - a larva that has pupaed and is heading to the surface to hatch

Adult - Sexually mature adult


Nymph - Zebra nymph

Pupa - MD-40

Adult - Griffith Gnat



Grasshoppers, beetles and ants should be a staple in any fly fishers box. These fly fishing bugs are just as important as mayflies and caddis when fishing in the summertime. Most of the flies are easy to see and will bring splashy takes from the fish. A nice part about a large foam grasshopper fly is that they can support a heavier nymph making them ideal for a dry/dropper rig.


Grasshopper - Dave's Hopper

Beetle - Bank Beetle

Ant - Hi-Viz ant

Top of Fly Fishing Bugs
Casting a fly rod
Fishing Grey Reef
How to Fly Fish