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3. Nymph ID please

Need help with ID of this nymph. I know picture is not the best quality.
Behavioral note this fellow was a very strong swimmer.
JW

Looks sort of like a Siphloplecton or Isonychia nymph too me.

Hi John & John,

I agree about the possibility of the first suggestion. It looks like it could be Siphloplecton basale (Pseudo Gray Drake). Isonychia nymphs aren't marked like this, shaped like this, and their gills aren't so prominently tracheated. Also, the forelegs are more prominent and hairy.

Was the underside pale with a thin dark stripe running down the center?

Looks a bit like Siphlonurus, but Siphloplecton will have forked claws where the former has a single claw.

Paul,


Yes, and frankly more than a bit.:) Siphlonurus is certainly another possibility and they are far more common. They can also have noticeable gill tracheation but they (gills) are shaped entirely different than Siphloplecton (heart shaped, much wider at the apex and doubled up) at least on the first few segments. The margins of siphlonurid gills are clearly noticeable with some cloudiness to the membranes, whereas Siphloplecton's are so transparent that in the right lighting they look just like old dead branches waving in the water. The gills in this photo certainly look to be denser in the first couple of segments, signaling Siphlonurus. Like the claws though, they can't really be made out. The heavy tracheation and lack of sclerotized band on the gill margins definitely rules out the similar looking ameletids, so it's between these two...

Looking directly down, Siphlonurus usually has tails approaching abdominal length with the abdomen comprising a little more than two thirds total body length. Siphloplecton on the other hand, will have tails substantially shorter then abdomen length and the abdomen will take up as much as 3/4 total body length. The angle of the photo coupled with the fore lengthening affect of the body parts closest to the lens makes it difficult to tell. It's hard to describe, but the two have distinctly different silhouettes. Here are two examples that John can use to perhaps jog his memory.
Siphloplecton
http://flyfishingentomology.com/forum/Replies_Display.php?t=0049
Siphlonurus
http://www.troutnut.com/specimen/997

John, where did you collect it? Clark's creek perhaps?

Eric -
I was hoping you'd chime in. What do you think? No fair waiting for John's response to all the goings on... You're a local for Pete's sake! :)

Unfortunatly I did not collect the sample nor did I ever see it beyond the picture posted above. This was collected by a friend of mine who is doing some work on a very small limestone influenced stream on his property.

Eric this stream is about 75-80 miles SW of Clarks and the particular run this guy was harvested in typically goes dry in the summer (actually a runoff trib to the stream he is working on). I have an invite to come back and fish the larger branch this week so we may need to try and capture another for further photographic studies.

My gut reaction was that it was an iso based on how strongly it swam in the video my buddy took but then the distinct lack of the dorsal stripe and coloration differences caused me to doubt that hence my post here. Let me also add that my typical ID process goes something like Spences' Little yellow bug system so counting gill truncations or describing their shape is beyond me.
JW

John,

Based on your description of the habitat, I think Paul's suggestion of Siphlonurus (Gray Drake) is closer to the mark, especially if Eric agrees. I don't know much about metretopodid life history but I do know that siphlonurids love to migrate out of main stems to hatch; even flooded bogs or the merest trickles that dry up in the Summer.

been watching to see how this would play out; i've been suspecting Siphlonurus, and the habitat is right

I think you guys pretty much covered it all without me! Now that I know the habitat,I'd call it Siphlonurus too. Pretty brave of me I know :)... The only place I know of in my area that has a fairly good population of Siphloplecton basale is Clarks creek, which is why I was trying to find out if it came from there. I thought it looked a little "stout" to be Siphloplecton but the angle was weird.

Well there you go, John. Pretty good consensus built on Siphlonurus.
Sorry John (WIflyfisher)... I tried to keep you in the game, but no cigar. :)