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Specimen Discussion

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The Specimen

The Discussion

Taxon	July 7th, 2006, 11:49 am
Site Editor Mercer Island, WA Posts: 921	Jason- Not to despair; this is what American Stoneflies: A Photographic Guide to the Plecoptera by Bill P. Stark, Stanley W. Szezytko, and C. Ridley Nelson has to say about genus Arcynopteryx: "This genus is represented in North America by A. compacta (McLachlan). This species ranges from Alaska to Maine and has been reported as far south as Colorado. Males usually have shortened wings and are easily recognized by the long, lash-like epiproct tip. Females and nymphs are quite similar to Skwala. A. compacta has been collected around alpine lakes in the northern Rocky Mountains. No photographs are available for this group." Also, Arcynopteryx compacta is listed by Stark/Baumann as residing in New York.
	Roger Rohrbeck www.FlyfishingEntomology.com
Troutnut	July 7th, 2006, 12:08 pm
The Admin Fairbanks, AK Posts: 2021	Thanks! It's probably A. compacta then. I like the genus name.
	Jason Neuswanger The Troutnut
Myersl	April 8th, 2010, 7:26 am
Plattsburgh, NY Posts: 5	Jason, This appears to be Cultus verticalis, although without examining the actual specimen or seeing adults, I can’t be sure. The color pattern is very striking in comparison to nymphs preserved in ethanol. I have collected adults of Cultus verticalis and Cultus decisus decisus from several streams in the Catskills. There are two species of Cultus in New York, Cultus decisus decisus (in large rivers) and Cultus verticalis (in small to medium sized streams). Arcynopteryx compacta is very uncommon in NY.
	myersl
Entoman	November 9th, 2011, 5:02 am
Site Editor Fair Oaks, CA Posts: 782	Great photos, Jason. There seems to have been a lot of back and forth on this determination over the years. I stumbled across these conversations while researching something else and quickly became interested. Trying to tie three different threads together back into one conversation is probably impossible, but worth a try. How they got separated in the first place, I have no idea. Anyway, the fortunate thing is that your quality photos teamed up with a good specimen (that shows some key characters unambiguously) makes this fun and worth revisiting. Perhaps the most important set of characters helpful in separating out the various genera of the Perlodidae can be found on the mesosternum and somehow they weren't discussed much regarding this specimen. The third photo shows these characters in great detail. FWIW, here's my two cents on the three genera possibilities mentioned, two that weren't, and another one that is a possibility: Arcynopteryx - This genus can be ruled out because its mesosternal Y-arms connect to the furcal pits at the anterior margins. Your photo clearly show the Y-arms connecting to the posterior margins. Cultis - In the West, this is a fairly common genus known as one of several Little Yellow Stones or Yellow Sallies. Anglers can usually distinguish these from other perlodids with the naked eye by their larger middle abdominal segments (giving them a bowling pin shape) and their sharply contrasting abdominal bands of pigment. They also usually exhibit a yellow band across the head's posterior margin and don't have oval pale spots between the eyes. These are traits clearly at odds with this specimen. The merits of "angler's naked eye perspective" aside, Cultis does not have submental gills projecting 2 times or more as long as basal diameter or a transverse suture connecting the fercal pits, while your specimen clearly does. Diura - While having the oval pale spots between the eyes and a similar dorsal habitus, this genus is eliminated because it also lacks submental gills and a transverse suture connecting the fercal pits. Also, it has not been reported south of New Hampshire. Isogenoides - This sure looks like it's right when comparing your dorsal photo to the few photos of specimens on the web that are also claimed to be in this genus. The terga and head markings match them to a tee. But this genus also has a problem related to mesosternal characters. Isogenoides has a median longitudinal suture running from the stem to the transverse suture between the Y-arms creating a three point contact. Your specimen lacks this character. Could the few examples available on the web that match your specimen so well be identified incorrectly? Isoperla - While most examples have longitudinal abdominal stripes, there are a few that don't. Regardless, they either lack submental gills or they barely project, and they do not have oval pale spots between the eyes. Both characters are at odds with your specimen. Malirekus - This genus meets the required mesosternal characters displayed in your photo. It can also have the submental gills 2 times as long or longer than their basal diameter (as per your specimen), and the oval pale spots between the eyes. The only species reported for the Northeast is iroquois. A few final points - Terga and head markings are so variable in this family that other than longitudinal terga bands and oval pale spots between the eyes, (and one example of frons pattern used to determine between two obscure genera) they aren't relied upon in the commonly used dichotomous keys. This specimen seems pretty large for the typical perlodid, rivaling the West's big Skwala species in size. Information regarding the relative size of these critters might prove interesting. Regards, Kurt
	"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman

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