Mayflies Moving

Exploring the Mayfly and Fishing

Often this time of year one will find the intriguing sail-shaped winged fly that arrives on shore from the water. There are signs of their emergence on the water surface on the lake shoals. On lakes, there are two varieties fly fishermen try to imitate, the Callibaetis and Tricorythodes or “Tricos” in the Midwest. There are other kinds of mayfly to consider, though not as great in numbers. One of the largest hatches in the world occurs also on our lakes, the Hexagenia limbata, inhabits silt beds and emerges in June to August. Known as the Hex hatch, these giant mayflies are found on the water only after dark. Large fish will rise to feed on similar species such as the gray drake. The famous Adam’s fly is perfect for fishing the gray drake hatch. Never shine a light on other anglers if possible as this may affect the fishing. I have yet to explore the possibility of using a red headlamp. Some insects do not gather to other light colors and some appear to be influenced by red.

To find these insects it takes some study of the methods to capture and identify them. Mayflies are found in a variety of forms and sizes. Generally, some are built for clinging or crawling, others swimming or burrowing. Certain features on the mayfly nymph can be used to identify the type and species. It takes a dissection scope to get the high detail to learn exactly what species. Mayfly can be fun and easy to find. Use either a small net with about ½ mm mesh or simply turn over the beautiful Michigan gravel to find a delicate mayfly. Sometimes in lakes with fresh water flowing there will be hundreds in a square foot or more!

 

Mayfly generally will have three tails but not always and may have two like a stonefly. Stonefly will have two tarsal claws, unlike mayflies, which is why a scientist may need a microscope to tell the difference. Most mayfly nymphs will not be very large, some only a few millimeters and others around thirty millimeters. Stonefly can be much larger, with their gills underneath their bodies. Generally to find more macroinvertebrates, search the littoral zones (shoreline) which are comprised of submerged and floating weeds or aquatic flora. Macroinvertebrates use the plants for shelter and food. Mayfly cannot be found in areas of high pollution and low oxygen. Mayflies have gills to breathe on their abdomen and live generally where there is a current of flowing water. Where you will not find as many macroinvertebrates of any kind is in the sand.

 

One can tell if a mayfly is a clinger or crawler by looking at the length of body proportions. Compare the head and thorax to the length of the abdomen. If the front portion of the mayfly is larger it is built for clinging or crawling. Others with longer abdomens will use it to swim and “wiggle” which is where “wigglers” get their name. If you find a
mayfly with a long abdomen and tusks on its head that means it burrows in the silt like our Hex fly hatch.

 

To identify the hatch use a pocket guide like “The Mayfly Guide” by Al
Caucci, a perfect tool for identifying the hatch. Other than an introductory textbook for a university, this little guide is waterproof and handles many of the details necessary to fly fish. Drop the mayfly right on the pages to compare. There are also other online resources such as The Bug Guide from Iowa State University and those which document the biotic indexes of Michigan lakes, giving the names and range of mayfly species. With all these tools and a quick assessment of the littoral zone, fauna should make a well-prepared fisher.

Beaver Island, MI

Special thanks to Wayne for the Hex fly image and movie.