I celebrated New Years Day by going to a tiny, slow water stream in Sugar Hollow and was rewarded by finding a pronggilled mayfly nymph, genus Leptophlebia. This is only the second time I've found a nymph of this genus, the first was in December of 2012. This one.
We can ID these nymphs to the level of genus by looking closely at the gills.
Gills on segments 2-7 on Leptophlebia nymphs are bilaminate, meaning they have two leaves on each gill, each one ending in a thin, string-like filament. Here's a microscope view.
Having not saved the nymph I found in 2012, I was excited to find this nymph so I could work out the species ID, though admittedly, the one I found on Wednesday might not be the same species as the one I found 2012.
So what did I find? My findings suggest that this is either L. cupida or L. nebulosa (the two species cannot be safely distinguished as nymphs). However, the two keys that I use both describe features for this ID that I can't be sure that I see: my microscope doesn't provide the magnification that I need. More on that as we proceed. Here are the information I've found.
1. Larvae of the Southeastern USA: Mayfly, Stonefly, and Caddisfly Species (Clemson University, 2017), pp. 138-139). The couplets are these.
259 Abdominal terga with numerous spinelike setae on lateral margins ........260
259' Abdominal terga with very few or no spinelike setae on lateral margins..........262
Let's look at our nymph.
There are indeed, numerous spinelike setae present. On to couplets 260 and 260'.
260 Forelegs with broad tibial and tarsal banding as in Fig. 2.423; inner margin of forefemur with considerable palmate setae (Fig. 2.424) ....Leptophlebia intermedia
260' Forelegs without broad tibial and tarsal banding (if banding present, then much narrower or much fainter); inner margin of forefemur with numerous serrate setae with small serrations on one or both sides of setae (Fig. 2.425) .......... 261
Look at the tibia and tarsus.
There is a dark area medially on the tibia, but it is clearly not a band, and there is banding at both ends of the tarsus, but it's clearly narrow and faint. On the setae on the forefemora, the magnification of my microscope is not strong enough to let me determine the shape of that setae (though I can see it). But since there is at the most faint banding of the tibia and tarsus, I'd conclude that we should move on to couplet 261/261'.
261' Labrum typically with dorsal surface setae as in Fig. 2.427 ............. Leptophelbia nebulosa
The figures in question (on p. 139) both show setae covering the labrum, but the illustration for L. nebulosa has a dense area of setae in the upper half of the labrum, an area that is missing on the L. cupida nymph. While I am able to see the setae covering the labrum, I cannot determine if that dense area of setae is present or absent. Moreover, our key adds the following note: "It may not always be possible to differentiate the larvae of L. cupida and L. nebulosa. Rearing to obtain the more easily differentiated adults is advisable."
If my logic is correct, our nymph appears to be either L. cupida or L. nebulosa, but that's as far as we can go. Having reached that conclusion, I decided to see what Steven Beaty had to say.
2. Steven Beaty, "The Ephemeroptera of North Carolina," p. 78. Here are his descriptions.
cupida -- nymphs 8.9-13.2 mm; peg-like setae on palpifer (small basal segment of maxillary palp) usually in regular rows; many large spine-like setae along lateral margins of abdominal segments along with scattered long hair-like setae; legs not usually banded or with faint bands on tibiae and tarsi only. Note: need to slide mount mouthparts and legs to separate from L. nebulosa which still may not guarantee correct species identification.
nebulosa -- nymphs 7.1-12.5 mm; peg-like setae on palpifer (small basal segment of maxillary palp) usually in regular rows; many large spine-like setae along lateral margins of abdominal segments along with scattered long hair-like setae; legs usually faintly banded or with faint bands only on femora with more distinct bands on tibiae and tarsi. Note: need to slide mount mouthparts and legs to separate from L. cupida which still may not guarantee correct species identification.
This is tough. We've already seen that there are "large spine-like setae along [the] lateral margins of the abdominal segments along with scattered long hair-like setae". All well and good. On the legs, there does appear to be faint banding on the femur, though it isn't complete, and I can't say that the banding on the tarsus and tibia is any more distinct. For the "peg-like setae on the palpifer," I think I can see it, but once again my microscope magnification won't allow me to confirm that let alone try to take a clear photo (I tried!).
Kind of stuck. I do think it's safe to conclude that our nymph is either cupida or nebulosa, but there's no way to go beyond that without a microscope with greater magnification. And even with that, we probably need an adult to be certain of our ID.
_____________
One other thing about this nymph.
Check out those eyes.
This "double eye" feature is something we also see on occasion on Baetidae nymphs, and it indicates that this is a male. The brown eyes on the sides are "compound eyes" that allow the nymph to see in various angles, the red eyes in the middle are "tubinate eyes" and are used by the adult mayfly to see directly above itself. They allow the male to pick out the females during mating. Very useful!
________________________
My photos can now be found on Instagram. My IG name is "buddhabob2hanlubo". I'll only be using this blog to post info on the new species I find, working out the species ID.
No comments:
Post a Comment