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Eastern Dobsonflies Emerging

7-9-18 male dobsonfly2_U1A0727

Eastern Dobsonfly (Corydalus cornutus) larvae, known as Hellgramites, are the top invertebrate predators in the rocky streams where they occur. In this stage they look like underwater centipedes and consume tadpoles, small fish, and other young aquatic larvae. Adults keep watch over them from a nearby area above the water.

After leaving their stream and pupating on land, the 4”-5 ½”-winged adults, referred to as Eastern Dobsonflies, emerge. Males can easily be distinguished from females by their large, sickled-shaped mandibles which the females lack. (The short, powerful mandibles of the female are capable of giving a painful bite, which the males’ mandibles are not.) Adults are primarily nocturnal and they do not eat. During their short lifespan (about three days for males, eight to ten days for females) they concentrate on reproducing.

The elongated jaws of the male are used both as part of the premating ritual (males place their mandibles on the wings of the females) and as weapons for fighting rival males.   (Thanks to Clyde Jenne for photo op.)

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8 responses

  1. Bill on the hill

    Here today, gone tomorrow… That is an incredibly short lifespan Mary, even for an insect!
    Great post once again…
    Bill Farr…

    July 9, 2018 at 8:02 am

  2. Marilyn

    Hellgramites, a jog from my past. Fishing? Must be an imitation lure: they might be painful to handle as bait, yes?

    July 9, 2018 at 8:15 am

  3. Alice Pratt

    Interesting, but odd insect.

    July 9, 2018 at 8:36 am

  4. Kathie Fiveash

    Hi Mary! I am finally resettled, getting ready to turn my attention to my regular life! In what sense do the adult dobson flies watch over the larvae?Is it protective in some way, or do the adults just stay streamside in order to be close to their egg-laying place?

    July 9, 2018 at 9:14 am

    • Hi Kathie,
      I’m afraid I don’t know any more than what I wrote. A reliable source mentioned that they keep an eye out for larval predators, but their life span is so short, as a reader pointed out, that I am surprised any of it is taken up this way, and not procreating…if I find out anything more, I will let you know. Great question. Best to you. m.

      July 13, 2018 at 1:02 pm

  5. cdhd2017

    One of these huge flying (I’ll guess male) bugs flew into our cabin at night on June 8th in Tennessee. We were on a lake cabin and I’ve never seen such a huge bug. After looking this bug up I was relieved to here they don’t eat and he wouldn’t hurt me. I’m learning from you that I could have not such an encounter with a female. They fly very fluttery and poorly. My husband caught him in his hat and took him back outside.

    July 9, 2018 at 7:07 pm

  6. Cathie Murray

    I first met adult Dobson flies while working at the Friends Camp in China Maine a few years ago. They regularly showed up in the outdoor sinks after a night with the lights on by the bathrooms. I was amazed I had lived 60+ years without every encountering them! Like the reader above, I am confused by your comment about the adults watching over the larval stage, as the larvae become adults and then don’t live very long. However, I am going to try to observe them in their larval stage…they sound quite impressive!

    July 9, 2018 at 10:17 pm

  7. Sharon Wogaman

    You took a picture of this. On the Blue line

    On Mon, Jul 9, 2018 at 3:45 AM Naturally Curious with Mary Holland wrote:

    > Mary Holland posted: ” Eastern Dobsonfly (Corydalus cornutus) larvae, > known as Hellgramites, are the top invertebrate predators in the rocky > streams where they occur. In this stage they look like underwater > centipedes and consume tadpoles, small fish, and other young aquatic ” >

    July 10, 2018 at 12:07 am

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