Western Dobsonfly? (Corydalus cognata) - Neohermes californicus

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Home » Guide » Arthropods (Arthropoda) » Hexapods (Hexapoda) » Insects (Insecta) » Alderflies, Dobsonflies, and Fishflies (Megaloptera) » Dobsonflies and Fishflies (Corydalidae) » Fishflies (Chauliodinae) » Neohermes » Neohermes californicus

Photo#307259

Copyright © 2009 Karen Rathbun

Western Dobsonfly? (Corydalus cognata) - Neohermes californicus

Placerville, El Dorado County, California, USA
July 20, 2009
Size: About an inch

I'm guessing this is a Western Dobsonfly - Corydalus cognata - but would like confirmation. Also, can anyone tell me why it was writhing as if in agony? I could not see any ants biting it or anything. I suspect a lizard got it when I left to fetch a different camera. One of the photos shows its mouth -- are those its mouthparts or was it extruding something? Also, I thought the larvae live in trout streams and it would have to come down from the mountains if it was birthed in a trout stream. We are having our usual dry hot July. (Yesterday at the house it got up to 101 F.) This is a woodsy area - lots of ponderosa pine and black oak. This is the second individual of this species I found here today.

Images of this individual: tag all

Western Dobsonfly? (Corydalus cognata) - Neohermes californicus

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Contributed by Karen Rathbun on 20 July, 2009 - 1:53pm
Last updated 3 December, 2010 - 5:20pm

Moved

Moved from Dobsonflies and Fishflies.

Several comments had this identification pegged. Moniliform antennae place this as Neohermes. The structure of the male genitalia place it into N. californicus -- namely, the apical structure (anal plate) is decurved and bifid.

… Brady Richards, 3 December, 2010 - 5:20pm

Protochauliodes?

I followed the key in Aquatic Insects of North America(1).

1. M vein of fore wing with 2 branches (not 3): 2

2. Posterior branch of Rs simple (not forked) in both pairs of wings: 4

4. M vein of hind with with 3 branches (not 2) reaching wing margin: 5

5. Crossvein absent between R3 and R4 of fore wing: Protochauliodes.

Sometimes crossveins are faint. If the vein is present but faint the key says Neohermes

… John F. Carr, 15 November, 2009 - 4:50pm

Moved

Moved from ID Request.

… Charley Eiseman, 21 August, 2009 - 3:58pm

Fishfly.

Not a dobsonfly, but a fishfly in the same family. I can't give you a genus, but someone else might be able to. I suspect this is either a defensive display, or a female that is emitting a pheromone from the end of her abdomen to "call" a male. Very interesting series of images just for the behavior alone!

… Eric R. Eaton, 20 July, 2009 - 3:14pm

Gray Fishfly - Neohermes californica

Thank you! I checked for photos on What's That Bug and found this, identified as a California Dobsonfly, Neohermes californica : http://www.whatsthatbug.com/2008/08/04/gray-fishfly-possibly-california-dobsonfly/
Maybe she was displaying or emitting a pheromone, but she sure looked like she was in agony. The photos I posted show her lifting her abdomen in the air -- and sometimes she almost looked like she was trying to touch her thorax with it! (Like a scorpion trying to sting itself.) But perhaps almost as often she curved it downward, arching her back, and once she flipped upside down for a few moments with her contortions.

… Karen Rathbun, 20 July, 2009 - 3:51pm

Neohermes

I suspect that "she" is actually a he. The antennae and the abdominal terminalia appear to be male. The strange behavior/posture is similar to mating displays described for Platyneuromus soror (noted on the Megaloptera page of the TOL website), and notice Patrick Coin's comments here.

… Lloyd Gonzales, 20 July, 2009 - 6:39pm

Male claspers

Thanks, Lloyd. I have added a collage-image showing the claspers from three different photos of the animal I saw.
Karen

… Karen Rathbun, 20 July, 2009 - 7:43pm

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