Mushroom-headed Mayfly

On June 19 I stopped by at the Berkshire BioBlitz at Canoe Meadows Wildlife Sanctuary in Pittsfield, MA, after spending the morning conducting a rare plant survey in Stockbridge. Whereas last time I photographed every bug I could and barely left the parking lot, this time I focused on leaf mines and galls. However, this little (~6 mm) mayfly was sitting so nice and still that I couldn’t resist taking a few photos:

My knowledge of mayflies is such that the big eyes told me this was a male, and that’s about it. When I got a side view and zoomed in to see if it was in focus, I saw that there was something weird about this one’s eyes.

It seems to be wearing these giant red eyes as a hat, on top of some “normal” compound eyes.

It turns out these “turbinate”  eyes are characteristic of the small minnow mayflies (Baetidae), which are the largest family of mayflies in North America. The compound eyes of male mayflies are usually divided, with larger facets above and smaller facets below, but in other families the upper ones aren’t raised on unfaceted stalks like this. (In this front view you can see that there are also three simple eyes, or ocelli, the outer ones partly obscured by the antennae.)

Roger Rohrbeck tells me this mayfly is Callibaetis ferrugineus ferrugineus. For comparison, take a look at the eyes of this female baetid (Plauditus sp.)…

…and the un-mushroomy eyes of this male from another family (Heptageniidae: Stenacron).