Because I fly fish, mostly for trout, I pay attention to what trout eat. In clean, clear water such is in the streams, rivers, ponds and lakes in and around Yellowstone there are a lot of aquatic insects, caddisflies, salmon flies, mayflies, damselflies, and dragonflies. Today I want to concentrate on mayflies, my favorite aquatic insects.
Mayflies start their life as eggs deposited in clear, clean, highly oxygenated water. The eggs hatch in a few weeks into a small nymph. The nymphs eat algae and detritus.
As they grow they molt several times. Some mayflies stay in the nymph stage for several months, a few spend several years.
When they are ready to change to a sub-adult they float to the water’s surface, their exoskeleton splits length-wise along the top and the sub-adult emerges. If it is lucky it flies away to land on a streamside bush, if not it gets eaten by a trout. The sub-adult is called a dun and lives 24 hours or less. Duns are called sub-adults rather than adults because they are not sexually mature. They are easy to recognize because they have wings that look a little like foggy glass. They are not totally clear. They have one job and that is to change into a sexually mature adult so they can reproduce.
To become sexually mature they shed their exoskeleton one last time, fly up in the air, and mate. The male then falls to the water and dies. The female lays her eggs and then she dies as well. Both the sub-adult and the adult are so short lived they don’t even have mouth parts or a digestive system, so they can’t even eat. All they do is reproduce and die. Fly fishers call this last part a spinner fall. It is highly anticipated by both fly fishers and fish because the dead and dying adult are sitting ducks. Male adult mayflies have huge eyes in relationship to the size of their body. I guess that is so they can spot females and quickly mate with them. My husband uses a Zeiss microscope lens to photograph mayflies close up. The photo below is actually over 100 photos he took at slightly different focus distances. He then stacks them together so that only the focused portion of each image is part of the resulting photo. As you can see male adult mayflies have 2 compound eyes. Vision must be really important to them!
Thank you Barbara! You need to get some sleep!
Yikes Verne! What a macro. And what a fascinating story Judy. Thank you.
Thanks Deby. Verne loves doing macro. You should see his fruit flies, but those are difficult to get into a conversation about Yellowstone.
Great lesson! Thank you!
Thank you!
Judy and Verne your photos continue to amaze me. The stories are so informative and interesting. It’s late at night, 11:21PM and the last thing I do before going to bed is look for stories in The Yellowstone Daily to see what I will find to see and read. Thank You and good night