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Two Taeniopterygidae taxa: Taenionema and Oemopteryx are difficult to identify, especially when larvae are not late instars. We have consulted multiple taxonomic experts to gain insight on ID characteristics, ecology, and habitat preferences of these genera. Consult the Expert Input tab for additional information.


The SLIMS database has 3 possible entries for these genera: Oemopteryx, Oemopteryx/Taenionema, and Taenionema. All records in the SLIMS database were retrieved and are displayed in tabular form (Sample Table tab) and as an interactive map (Sample Map tab). The samples table is intended as a quick reference to determine samples containing either genera if re-examination of specimens is desired. The samples map allows examination of the spatial dynamics related to the occurrence of each taxon.

Expert Input

Dave Rebuck (PADEP Retired), Mike Cole (Cole Ecological, Inc.), Ed DeWalt (Illinois Natural History Survey), Mike Bilger (USGS Retired), and Scott Grubbs (Western Kentucky University) were consulted for insight into Taenionema and Oemopteryx. The following is a summary of their responses, broken out by topic.


Deficiencies with existing keys

  1. The key characters and illustrations in Stewart and Stark, Merritt, Cummins & Berg, Morse et al., and other references are primarily based on western and northern species, rather than the Oemopteryx contorta and Taenionema atlanticum that we have in Pennsylvania. I haven’t found the body and leg coloration characters in the keys to be reliable for identification, because there is too much variation between instars and specimen quality. Contrary to the keys, both O. contorta and T. atlanticum have dorsal head spots, but there are slight differences between the species, so that character can only be reliably used if taxonomists know how to interpret the differences. The differences between the shapes of the pronotum are minimal and variable. Very unfortunately, for the most frequently used morphological character (shape of the 9th sternite), the descriptions and illustrations of the the ninth sternites in male and female larvae in the references are also based on species not found in Pennsylvania, so they are completely wrong for O. contorta and T. atlanticum. Jane Earle’s key is the best, but she uses the incorrect illustrations of the 9th sternites from Stewart and Stark. - D. Rebuck 2022

  2. As far as ID, my experience with these two tells me that the most commonly used keys are not entirely accurate with their descriptions of the color patterns (or lack thereof) on Taenionema and Oemopteryx. Specifically, MC&B, and Morse et al both describe Taenionema as “body and legs brown, with indistinct pattern” and Oemopteryx as “body and legs lighter with distinct pattern”. In contrast, Jane Earle, who has collected extensively in PA, describes Taenionema as “Usually brown, with darker pattern body and spots on rear of head” and Oemopteryx as “Generally uniformly brown, rarely has darker small dots on head and protnotum”. Note that the descriptions by Earle are almost opposite those of the other keys! Don Chandler’s unpublished New England stonefly key describes them the same as Does Jane Earle. Effectively, Earle and Chandler describe Taenionema as having distinct patterns, while Oemopteryx is either uniformly brown or has indistinct patterns. Furthermore, the 2002 Stewart and Stark key does not even allow for direct separation of O. contorta from Taenionema because the key does not account for the fact that O. contorta lacks the dorsal fringe of fine hairs on the basal cercal segments. As a result of these two issues combined, an unknown number of Taenionema records are potentially actually O. contorta! (and vice versa, as well). - M. Cole 2023

  3. I am likewise not a fan of the characteristic that Bill Stark chose for separating Oemopteryx from Taenionema. He is correct that Taenionema larvae are generally brown with little contrasting pigmentation, as also in Stewart & Stark (1988, 2002), but alcohol can play tricks with pigments and potentially lead to misidentifications. This is especially so for immature larvae. I am also not a fan of interpreting pronotal shapes. Specifically, I presume the biggest challenge is differentiating between Taenionema atlanticum and Oemopteryx contorta, both of which I presume are generally common throughout much of Pennsylvania. Both species lack the dorsal hair fringe, as you know, along the basal cercal segments. - S. Grubbs 2023


Habitat Preferences

  1. In my experience, T. atlanticum are rarely found in small acidic, 1st and 2nd-order freestone streams… - D. Rebuck 2022

  2. Generally speaking, T. atlanticum occurs in medium-sized creeks, but it can definitely occur in smaller creeks. O. contorta is typically associated with small streams, and particularly in acidic creeks, but can occur in medium-sized creeks, particularly if not too warm. This is all to say that O. contorta would typically occur further upstream in a drainage network than would T. atlanticum, but their distribution can overlap (this info primarily comes from Jane Earle, not my personal observation). - M. Cole 2023

  3. I am unaware of general habitat preferences. For Maryland, in Ridge & Valley streams, we would only find T. atlanticum (not O. contorta). That said, Maryland is a tiny state compared to Pennsylvania and I think it is difficult making too many inferences from only one county. - S. Grubbs 2023


Reliable ID Characteristics

  1. In my opinion, the best character by far to separate the two genera is the shape of the paraprocts in male larvae, because they are completely different in O. contorta and T. atlanticum. - D. Rebuck 2022

  2. If one really wants to dig into these two taxa and learn them, slide mounting of the mandibles is necessary. On Taenionema, the mandibular tuft of hairs will NOT extend out to or along the low, flat molar area (see SEMs in Stewart and also my photos attached). - M. Cole 2023

  3. Similar to working through identifications with immature larvae of Yugus and Malirekus (lacinial characteristics), for Appalachian Oemopteryx vs. Taenionema I occasionally have to remove the mandibles and examine under higher magnifications (dissecting or compound). Oemopteryx mandibles are fringed with short hairs from the teeth to the base, whereas Taenionema mandibles lack a basal hair fringe. - S. Grubbs 2023


Taenionema left mandible


Taenionema right mandible


This tuft will extend out along the molar area on Oeomopterx. This character will allow confirmation of genus and also allow association of color patterns with each genus. - M. Cole 2023


Oeomopterx mandible


  1. In my experience of mounting mandibles, the color patterns consistently match those as described by Jane Earle (and Don Chandler). Oemopterx is generally brown with very indistinct patterns (sometimes no apparent pattern at all). Taenionema is a lighter brown and has distinct patterning on the head and thorax. See attached Ken Stewart’s 2009 revised description of Taenionema to see this. The illustrations clearly show a taxon that is mottled and not uniformly colored!! I’m also attaching some of Tom Murray’s photos that were confirmed by Don Chandler. They show the more distinct patterning on Taenionema as Earle describes and I’ve seen (and exactly as is illustrated in Stewart’s 2009 paper!). - M. Cole 2023


Oeomopterx photo (credit Tom Murray)


Taenionema photo (credit Tom Murray)


Click here to download Ken Stewart’s 2009 revised description of Taenionema


Sample Table

Sample Map