The Mayfly life-cycle

Brian,

I want to thank you very much for all you've done for Trout in the Classroom. You are very good at putting scientific matters on a level the students can understand. When you asked those questions, I was amazed because I hadn't seen your streamside activities before and those were very similar to the ones I used on May 10 with Providence Montessori Elementary at Lusby Lake in Scott County.

Since we couldn't search for aquatic microinvertebrates, I began with what is the difference between a creek and a river, followed by what is the difference between a pond and a lake. The answers surprised the students, especially since Lusby Lake looked like a pond. Then I asked them what had the students fed their trout fingerlings to make them grow so big and they answered with fish food. Then I asked them who is going to feed them out here in Lusby Lake and they didn't know. So that was the introduction to the life-cycle of the may fly which goes through a metamorphosis starting out as eggs, growing into larvae that may live 2 to 3 years in the stream breathing through gills underwater. Then at a certain temperature one spring or summer, they drift to the surface, sometimes on a bubble of air that comes from a split in their wing case or they swim to the surface and after they shuck their outer skin and thorax, they rest on the water's surface or a rock like stoneflies do to dry their wings as a dun. Once their wings dry they are adults and fly upstream to form a mating swarm then return to lay their eggs on the surface of the water. Then I asked, "Why do they fly upstream from where they lived for 2 or 3 years?" No one knew. When I told them they flew upstream because their eggs would float for a long time before they sunk to the bottom to hatch into larvae and more than likely it would be where they grew up and lived as a nymph. They asked, "How do they know to do that?" And I answered, "They don't make a decision to go upstream or downstream, it's just instinct." After they lay their eggs, they usually die within 24 hours and they fall to the waters with their wings spent and we fishermen call them spinners. I concluded with telling them that at every stage of their life-cycle, the mayflies, caddis flies and stone flies are a delicacy for trout. These three are rated as very pollution sensitive of the macroinvertebrates. Both trout and the insects they prefer are an indicator of water quality.

When I get back from my fishing trip with my son, Wade, we still have Poage Elementary at the tailwaters of Grayson Lake on May 26 and Phillip A. Sharp Middle School at Raven Creek just North of Morgan, KY turnoff on 303 on May 27.

Check out our blog at http://troutintheclassroomky.blogspot.com/ for pictures and stories of each trout release so far.

Thanks,

Don