Using My Degree in Entomology to Figure out what Fly Fishing is All About

Using My Entomology Degree to Figure Out What Fly Fishing is All About

If you’re like me, you may have seen fly fishing in movies, tv shows, or even real life and thought that it looked like a mindless tossing and whirling of fishing line bound to end up a twisted and knotty mess. After getting my bachelor’s degree in entomology—which is the study of insects that you can apparently get a college degree in—and relocating to a region where fly fishing is far more common than where I’m from, I decided to do a bit of digging into this hobby. I learned that there is quite a lot that goes into it.

Anglers who fish with flies often have a basic understanding of entomology. By learning a bit about the life cycles, behaviors, and appearances of certain insects, they can better their fishing abilities. Some of the most common insect groups used are Mayflies, Midges, Caddisflies, and Stoneflies. While most of these have the word “fly” in the name, the only one that is actually a fly is the Midge. Actual flies belong to the scientific order of insects called Diptera, which means “Two Wings,” 

because these flies are one of the only group of insects with two wings; most have four! Mayflies and stoneflies have what is known as an incomplete metamorphosis where they do not have any kind of distinct stages as they mature. They just slowly grow, eventually becoming a sexually mature adult that can fly. On the other hand, Midges and Caddisflies have what is called a complete metamorphosis with 4 distinct stages: the egg, the larvae, the pupa, and the adult (exactly like a butterfly). Most fly fishermen don’t really care about these scientific distinctions but use a basic understanding of these stages to fish by mimicking behavior. Often, fishermen call these stages nymphs/larvae, emergers, and dry flies. This piqued my interest because I wasn’t entirely sure what an emerger or dry fly was. Obviously, I had to figure out what they were and how fishermen use these stages differently.

Starting top left, clock wise around: Mayfly, Stonefly, Midge, Caddisfly. Photos credit respectively: Miles Zhang, Miles Zhang, user ESant of, Brittanica

Nymphs and larvae are the immature stages of insects with incomplete and complete metamorphosis, respectively. They are typically found on the bottom of streams and creeks under rocks, but they can also swim in the water column. To fish by mimicking nymphs and larvae, fishing flies are kept near the bottom of the streams. Emergers are the stage where the nymphs or larvae rise to the surface in preparation to emerge into their adult form. Fishermen mimic these by rising their fishing flies from the bottom to the surface of the stream. The final stage that fishermen refer to are the dry flies. These are the adult stage that rest on or fly near the surface of the water. The dry fly stage of Mayflies is broken into two unique stages: the non-sexual dun and the sexually mature spinner. The spinner is typically what is mimicked. Fishermen mimic the dry fly by keeping fishing flies on the surface with light bounces to imitate flying and landing. Different stages may be more active or abundant at different times of the year or in different environmental conditions, so fishermen use this knowledge to decide what stage to use when fishing. The “mindless tossing and whirling of fishing line” that I referred to earlier is actually the fishermen moving their fishing flies in specific patterns to mimic the behaviors in these different stages.


Life cycle of a Mayfly where the nymph will go through multiple non-distinct stages as it becomes more adult-like. All other insect with incomplete metamorphosis have the same lifecycle, though the subimago/dun stage is only in Mayflies. Photo credit: Aardvark McCleod


Life cycle of a Caddisfly with four distinct stages that all insects with complete metamorphosis go through. Larvae will maintain their same general appearance as they increase in size. Photo credit: Jonathon Richter on Pinterest

As someone with a formal education in entomology, it is super interesting to learn about the similarities and differences in the way entomologists and fly fishermen talk about bugs, and while I may not fully understand the tossing and whirling that is happening, I now know there is a method to the madness. These fishermen clearly know what they are talking about and what they are doing, which is unsurprising because outdoor recreationists are well versed and knowledgeable in what they do. While everything may not line up exactly with the scientific world, their knowledge is in no way incorrect. This just goes to show that there is knowledge in experience, and you don’t need a degree in bugs to know about or enjoy the fascinating world of entomology.

Jacob was a 2021 Naturalist for SIHA. He really likes insects, and you can often find him flipping over logs and rocks to look for critters. When he is not on the hunt for bugs, he enjoys spending his time hiking and exploring new areas.


(1) The 5 Bugs of Fly Fishing Entomology to Know? – (

(2) Fly Pattern Selection – Determining Fly Fishing Lures | What To Consider (

(3) Ephemeridae (Hexagenia limbata) | Miles Zhang | Flickr

(4) Common Stonefly (Plecoptera: Perlidae) | Miles Zhang | Flickr

(5) – Discussion Forum: Chironomidae: Chironomus sp.

(6) Caddisfly | insect | Britannica