Caddisfly ID help: I keyed to Limnephilidae . Onoscosmoecus or Eocosmoecus (see characters in Remarks)

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Home » Guide » Arthropods (Arthropoda) » Hexapods (Hexapoda) » Insects (Insecta) » Caddisflies (Trichoptera) » Unidentified Larvae, Cases & Pupae

Photo#900756

Copyright © 2014 Bruce Lund

Caddisfly ID help: I keyed to Limnephilidae . Onoscosmoecus or Eocosmoecus (see characters in Remarks)

Las Vegas , Clark County, Nevada, USA
March 11, 2014
Size: 20 mm

Stream pools in Mojave Desert through sand dunes and limestone substrates in Red Rock Canyon National Conservation Area. In keying the larva through Merritt and Cummins (Intro to Aquatic Insects of North America) to family, characters of the specimen include: anal claw hook-shaped, metanotum membranous, antenna not apparent, mesonotum covered by sclerotized plates,abdominal seg 1 clearly has lateral and dorsal humps, labrum w 6 or fewer setae, base of anal claw lacking brush of setae, median dorsal hump present > LIMNEPHILIDAE. Keying in the family key, characters include Mesonotoum w 1 pr sclerites, basal seta of each claw is short, abdominal gill present, pronotum and dorsum of head w/o hairs, abdominal gills multiple, gills gills 3 branched (not 4 or more branched) , dorsum of head uniform in color, metathoracic femur w more than 2 major setae, metanotal sa 1 sclerites separate, tibia w one pair of spurs, pronotum w submarginal setae evenly spaced and same length/thickness, case of rock fragments > EOCOSMOECUS (or Onocosmoecus)

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Caddisfly ID help: I keyed to Limnephilidae . Onoscosmoecus or Eocosmoecus (see characters in Remarks)

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Contributed by Bruce Lund on 14 March, 2014 - 12:03pm
Last updated 7 August, 2020 - 7:41pm

Moved

Moved from Caddisflies.

… Bob Biagi, 7 August, 2020 - 7:41pm

Moved

Moved from ID Request.

… v belov, 26 March, 2014 - 10:08am

Onocosmoecus or Eocosmoecus

Bruce, I'm more inclined towards Eocosmoecus because of the case and because Onocosmoecus usually has a light stripe through the center of the head, pronotum and mesonotum. The cases of Onocosmoecus, at least the ones I've seen, are primarily of wood. If you still have the specimen, check the setation on the dorsal pronotum as well as the setation on dorsal abdominal segment VII. These are both illustrated and described in Merritt and Cummins and should help you to differentiate between the two genera. If you don't have a copy of Merritt and Cummins handy I can email you a copy of the relevant illustrations. There don't seem to be any pics of Eocosmoecus in BugGuide but Onocosmoecus can be seen here (1), (2), (3), and here (4). In the meantime, with any luck Dave Ruiter may take a look at your pics and shed some light on the matter.

… Mark Melton, 15 March, 2014 - 10:09am

I do have my specimens and I

I do have my specimens and I added two macro images of the pronotum with setae to see if that will help. Without experience with both genera and just having the Merritt and Cummins illustrations to go by, I’m not confident deciding which setal arrangement I have on my specimen: I don’t have experience to judge whether the setae are “widely spaced” as opposed to “more closely spaced”, but in general they look more like Onoscosmoecus being of equal size and lacking shorter lateral setae. Also, I admit I cannot make out the abdominal segment VII setae. HOWEVER, because the case is constructed of sand grains, I decided my specimens are Eoscosmoecus.

I also had looked at the Onoscosmoecus images on Bugguide as well as searched on line for other images and didn’t find much to help there. See if my additional image helps.

… Bruce Lund, 16 March, 2014 - 12:00pm

The dorsal hump looks too pro

The dorsal hump looks too prominent to be either Eocosmoecus or Onocosmoecus, and I only see two major setae on the hind femur. I believe you may have taken a wrong turn. I like the Glenn B Wiggins guide as it has full illustrations for every genus.

… Rachel Bauer, 17 February, 2017 - 1:33pm

Pronotum pics

I'm still not able to tell for sure which genus your specimen is. Merritt and Cummins are a bit vague. I went back to my Onocosmoecus specimens and took a couple macros of the pronotum (1) and (2). Perhaps you can compare them to your specimen. I lean towards Eocosmoecus for the same reason you do, namely the case. I couldn't find any reference to gravel or sand cases for Onocosmoecus. I found some literature by Wiggins and Richards - Revision of the Onocosmoecus Unicolor Group (Trichoptera: Limnephilidae, Dicosmoecinae) and another paper - Biosystematics of Eocosmoecus, a New Nearctic Caddisfly Genus (Trichoptera:Limnephilidae, Dicosmoecinae) by Wiggins and Richardson. Both are available online though you'll have to register at JSTOR to read the one on Eocosmoecus. The paper on Eocosmoecus does have an excellent line drawing of a larva and it's stone case that looks quite similar to your specimen.

… Mark Melton, 16 March, 2014 - 5:46pm

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