Mayflies Should Be Normal
In April, I joined a class of Ames High School seniors to survey benthic macroinvertebrates in Ioway Creek. If you had asked me “what on earth are you doing?” here’s what I would have said:
Hello! I’m Dan and I work on water quality for a local non-profit. And these are environmental science students from Ames High School. Why are we standing in the middle of the creek wearing hip waders and doing what looks like a funny dance? Why, this is a perfectly normal thing to do! We are citizen scientists and we are “science-ing”! The dance is called the benthic shuffle, and is an important part of the protocol for biological monitoring. We are dislodging aquatic insects from the rocks and catching them in our net.
And look at what we have caught from a mere 1 square meter of rocks! 170 mayflies! This too is normal! We are at Brookside Park, and here is a brook babbling over rocks and gravel. It would be strange if we did not find a healthy population of mayflies in such inviting habitat!
No, they don’t look like the mayflies that spatter windshields in Dubuque. But this is indeed Baetis, the blue-winged olive mayfly, imitated with success by many a trout fisherman. In its larval form, we call it the “small minnow mayfly”, for its quick swimming. They live about a year in the creek before they pupate and get their wings, assuming a fish doesn’t eat them first!
As I was saying, what you see here is perfectly normal, though maybe not as common as it should be in Iowa streams. If you find a riffle in the stream with no mayflies, well, that would mean something is not right. Perhaps insecticides have washed into the creek from upstream farms and lawns and killed them. Perhaps we’ve inadvertently fertilized the algae in the creek, turned the water a shade greener and the making the water a little less oxygenated at night. There are other insects that can make a living under these conditions. In the creek near the Story County Fairgrounds, you can find plenty of these net-spinning caddisflies, but no mayflies! If all you find are these wriggly little midge flies, well, that’s a sign of more serious pollution.
Nice to meet you! Time to get back to counting bugs!
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