Wednesday, June 6, 2012
Baetis flavistriga: Another Summer Small Minnow Mayfly
We actually had a couple hours of sunshine today -- something that's been hard to come by in recent weeks -- so I made a quick trip to Mechunk Creek in Fluvanna county, just east of town. I was hoping to see some Stenacron flatheaded mayflies -- no luck with that. But I did find one thing to remind me again that it's summer. The small minnow mayfly, Baetis flavistriga. A couple more photos to look at.
I wish my photos were bigger and sharper, but this is a very small nymph. Beaty ("The Ephemeroptera of North Carolina," p. 6) has 4-6 mm for this Baetis species, and this one was 4 mm at most. Still, if you click on the photos, the detail should be fairly clear
Baetis flavistriga nymphs, as you look at them in a tray, look a lot like Baetis intercalaris nymphs which we're also beginning to see. But with magnification, we can easily tell them apart. The abdominal markings differ, so too do the bands on the tails (caudal filaments). Baetis flavistriga nymphs have "two large submedian kidney shaped spots on [the] abdominal terga," and the "caudal filaments [have a] medial dark band." (Beaty, p. 6) We can see those features best in a microscope view. (And note the length of the wing pads: this is not an immature nymph.)
Now here is a look at the Baetis intercalaris nymph that I found last week in Buck Mt. Creek.
There are three dark bands on the caudal filaments of B. intercalaris nymphs, and on the tergites, there are "paired pale submedian parentheses shaped marks" (Beaty, p. 6). These, too, are very clear in a microscope view.
Baetis intercalaris nymphs are also bigger than B. flavistriga nymphs, normally 5-6 mm in length.
Both species are "common and tolerant" (Beaty): B. intercalaris has a TV of 5.0; B. flavistriga comes in at 6.8. Can't say I'm surprised to find B. flavistriga in the Mechunk, it's not the best of streams.
I saw a lot of flatheaded mayflies today -- I always do in this stream. They were all Maccaffertium in terms of the genus, I'm not sure of the species ID.
I also found two beautiful Perlesta stoneflies, and I'll close with a look at those photos. One was very gold, the other one -- the more mature one -- more goldish brown.