Mayfly Genus Litobrancha

Okay, I'm at a local TU meeting and a friend tells me about a double secret mystery hex hatch. According to him, these hex are colored differently than our limbata, hatch two or three weeks earlier for about 3 days only (last week of May or the first week of June), and exhibit some other "different" behavior traits. Needless to say, I was interested in learning more. Fast forward to this morning when I picked one of the nymphs up from his house after he dug a sample up for me to take home. Its still alive, so I'm trying to figure out what body parts I need photographs of to share here to see what you guys think this guy is.

A quick look at the head and tusks is pointing me to Litobrancha recurvata, and the emergence period shown in Hatches II for them is about right (May 14 to July 3). The photo they have in their color plates looks very close to what I just finished photographing, but what I have looks different.

I took a couple dozen quick photos of it and uploaded them to my flickr account, wasn't sure if it was ok or necessary to upload them all here. Link to the gallery below. Please let me know if you'd like me to upload any of these here, or if you'd like a better shot of a certain feature, so you can see the full res photo for better detail. In my non-expert opinion, I would say this nymph is near full maturity, as its ginormous. I can't find my metric ruler, but it is ~50mm long. Thanks for any help.

http://www.flickr.com/photos/cerveniak/sets/72157633180659254/


Alex

Collected a couple of these last week. Pretty cool mayfly if you ask me!

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Sorry no photo
While out fishing I came across a big drake spinner. I think it might be Litobrancha Recurvata. 2 tails 17 mm body length, front pair of legs darker than back two, olive abdomen, darker thorax. Collected August 28th, which is relatively late for Litobrancha. Also could be Hexagenia Rigida or Atrocaudata.

Anyone know if Litobrancha or the Late Hexs are present in Southeast Mn?

Caucci and Nastasi's comments and other comments above are correct. They are really hardy and impressive nymphs when they near maturity. Litobrancha nymphs prefer fine silty, mucky habitats in streams. They can be abundant in mucky side channels to the main stream. Their emergence occurs over a 5-day span, with the large majority emerging within a 3-day period. Therefore, large emergences are rarely encountered. When they do occur, they can be very impressive.

From my experience collecting and rearing these critters, they have a 2-year life cycle in PA and MD. They increase tremendously in size in their second year. Emergence occurred in late May into early June about a week before that of green drakes (Ephemera guttulata).