Yesterday there were huge numbers of the Giant Mayfly (Hexagenia limbata) covering building surfaces facing the shoreline of Leech Lake in Walker Minnesota. The images below were taken on Walker’s public dock.
In the central image above, the Mayfly to the right is male and the one to the left is a female. Males typically are smaller, darker, and have larger eyes.
This species of Mayfly can be found throughout most of North America, but is most common in the Great Lakes region. There are several interesting facts about Mayflies.
- Mayflies are one of the first insect species to evolve, appearing more than 300 million years ago.
- As commonly known, they only live 1-2 days in their adult stage (imago), but can live up to two years in the nymph stage, and spend 2-3 days in a sub-adult stage (subimago).
- The yearly emergence of Mayflies from nymph to subimago stages commonly happens over a very few days. This results in thick swarms of mayflies, so huge that the swarms can be mistaken for storms on weather radar.
- Mayflies are a critical food source for fish in lakes and slow-moving streams, where they can comprise a significant proportion of the aquatic biomass.
- Fly fishermen study the habits of Mayflies closely, in particular the Hexagenia, known by them as the “Hex”. Avid trout fishers flock to northern streams when the Hex emerges in late June and early July.