Aquatic Insects:
Bugs 101, The Simple Lesson
by Richard Babine

That's talk real basic entomology or more specifically a beginning of understanding aquatic insects. The plain fact is that if you hope to catch fish on a consistent basis, instead of by chance, then you have to have some understanding of how this bug thing works.

The first lesson is that a fish will consume over 75% of its total food intake by finding its food source below the waters surface. Simple logic should suggest that an angler must take advantage of this fact of nature if the goal is to catch fish on a consistent basis. You have to learn something about the life cycles and habits of the major aquatic insects that fish eat. The largest reason for this is that if the fish eat 75% of their food below surface, this leaves the remaining 25% consumed at the water's surface. In case you missed my point, I'm telling you that unless you're in the middle of an aquatic emergence or the resultant oviposting, you're not going to catch anything on a dry fly.

The second lesson is that fish love the following food items; Caddisfly, Mayfly, Stonefly, Midges, Leeches, Shrimp, Crustaceans, other fish and even things that fall onto the water's surface. But the meal of choice is and always will be aquatic insects, so let's take a simple but effective look at these various insects and the roll they play in a fish's life. This lesson is easy to remember if you think about the water in terms of its' depth.

D = Diptera = Chironomids (Midges)

E = Ephemerella = Mayflies

P = Plecoptera = Stoneflies

T = Trichoptera = Caddisflies

H = Heavenly Bodies = Bugs and others that fall into the water

D
Dipoptera (True fly having two wings)
Chironomids (Midges)

Midges (Deerfly, Gnat, Cranefly, Blood Worm, Black Fly, Horsefly, and the ever popular, Mosquito) are tiny insects that have a life cycle similar to the caddis, that is to say that the stages are complete; egg, larval, pupal, and the air breathing adult. These insects are the most plentiful and smallest insects in our waters. The stages are different only with respects to the time the insect spends as a pupa. One large difference is the midge spends a much longer period of time attached to the underside of the surface meniscus before breaking through as an adult. These pupa also travel much greater distances before emerging as adults. These are often very small insects but at the same time are among the strongest in the aquatic insect kingdom. This is very evident when in fact these small insects will emerge from the water in temperatures that freeze other insects solid before they could reach the riverbank. As long as the water isn't frozen solid, these creatures will hatch. These insects are basically fished by using an emerger pattern and as a dry the fly of choice is the Griffith's Gnat. The more advanced anglers will also employ a rig system using the Griffith's Gnat as the dry and strike indicator and a dropper fly such as a Serendipity or Copper Buzzer.

Common Imitations:
Griffith's Gnat, Biot Midge, Copper Buzzer, Crystal Chironomid, Mosquito Pupa, Serendipity & Suspender Midge

E
Ephemerella (lives but a day)
Ephemeroptera (Up-right winged)
Mayflies

There are a gazillion species of the ever-popular Mayfly but you really don't need to know the Latin scientific name, genera, family and specific species to be a good angler. These insects are born into the air-breathing world without any functioning mouth, now you know why they live but a day. We place little cute names to these insects in order to separate one species from another. Some of these common names are Adams, Quill Gordon, March Brown, Pale Morning Dun, Blue Winged Olive and so on and so forth. Mayflies will deposit eggs onto and in the water, usually in or just above a riffled area. These eggs will sink to the bottom and eventually hatch into immature (baby) nymphs that live, feed and grow under the waters surface. The Mayfly is said to have an incomplete life cycle because it bypasses the larval stage by hatching from the egg as a nymph. Some will swim around aquatic vegetation, some will spend their lives crawling or clinging around rocks, boulders, weed clumps and other aquatic debris, while still others will burrow into the fine sand or silt and decayed organic debris that covers the bottom areas of slow flowing waters.

Depending on the specific species some Mayflies will take from a few weeks to a few years to mature to the point where nature forces them to the surface to enter the air-breathing world.

When nature calls, the nymphs will rise towards the surface and attach themselves briefly to the underside of the surface film in the emerger phase of its life cycle. Fish love these emerging nymphs and quite often even go into a feeding frenzy as though they understand that this free lunch won't last very long. Fish will not let a feeding opportunity go to waste and will always take advantage by selectively feeding on the most prominent species, letting anything else drift by untouched.

While slightly beneath or even in the surface tension, the nymph will attempt to separate itself from its nymphal shuck. This activity causes such a commotion that nearby fish will find it irresistible and charge the insect before it gets away. Once the insect sheds its nymphal shuck, it will sit on the waters surface and spread its wings. While the prevailing air currents are drying the wings, these small insects are looking much like small sailboats being blown around by the warm breezes. Fish also love to take these small offerings before they take flight and leave the waters surface. The dun will fly to the nearby trees or bushes and go through a final moult into a sexually mature spinner, so called because the mating in air requires an aerial spinning maneuver. At this stage, the insect's wings will loose all color and appear cellophane clear. Once mating has taken place, the female will deposit the fertilized egg onto or into the water, then dies and often falls to the waters surface as a spent spinner. The male will also follow the female by spinning towards the waters surface as a spent spinner. These spinning activities will also cause fish to take advantage of a feeding opportunity.

Common Imitations:
Adams, Blue Winged Olive, March Brown, Grey Quill, Quill Gordon, Hendrickson, Red Quill, Blue Quill, Grey Fox, Cream Variant, Light Cahill, Sulphur & Maple Syrup

P
Plecoptera (Folded wings)
Stoneflies

These are among the largest aquatic insect and at the same time the simplest. Like the mayfly, the stonefly has an incomplete life cycle. The stones only have two stages that are of any importance to us anglers and that is the nymphal and adult stages. The stonefly requires highly oxygenated water that is medium to fast flowing and has a streambed of small- to- large rock aggregate.

These aquatic creatures often have great periods of time between stages and can actually take over two years to mature enough to hatch into air-breathing adults. The nymphs, when ready will crawl from the water up plant stocks, boulders, rocks, logs, and anything else that will provide an avenue of escape from its aquatic beginnings.

Common Imitations:
Kaufmann Black Stone, Whitlock Stone & Michigan Caddis

T
Trichoptera (Hair covered wings)
Caddisflies

Caddisflies have what is called a complete life cycle, which is; egg hatching to the larval stage then through many moults the larvae develops into a pupa and the pupa will rise to the surface as an adult caddis, dry its' wings and very quickly fly off to the waters surrounding vegetation.

The mating ritual of the caddis is always the same. Between sunset and late dusk the males will return to the riffled areas dipping and skittering along just above the waters surface. The females will enter the mating swarm and after the nuptial activity is completed, will deposit her eggs by one of three methods. The female will fly just above fast water and jettison the egg sac onto the surface or the female will drag her posterior across the waters' surface to dislodge the eggs from her abdomen. Some species will even dive and swim to the bottom before releasing the eggs or crawl into the water by using the stock of an aquatic plant or a boulder, rock and even other debris that may have fallen into the stream.

After a time the eggs will hatch and the larvae will, depending on the species, be a free-living larvae that crawls around the bottom substrate, a larvae that will spin a spider like web or net and exist behind the net and there are other larvae that will collect fine gravel, organic debris and make a case which the aquatic insect will crawl inside for protection.

Each species will go through many moults before developing into the pupal stage and rise to the surface where it will attach itself to the underside of surface meniscus (tension). Once they moult into the adult insect, they break through the surface tension and quickly fly off to the surrounding vegetation to start the process all over again.

Common Imitations:
Brassie, Elk Hair Caddis, Caddis Sparkle Emerger, Cased Caddis, Caddis Pupa