Subject: Large Army Green Beetle
Location: Terlingua Ranch, West Texas
May 5, 2017 2:37 pm
We found this guy on top of our water catchment barrel in West Texas, next to Big Bend National Park. He was big enough to fit in a teaspoon, which I used to get him out. He sprang off the spoon with those powerful back legs. He didn’t attempt to fly, but it looks as if it has wings of some sort under that hard exterior. I am certainly curious about this one. We see so many unique insects out there, but this one is a mystery. I love his little eyes….
Yes, I did take this photo and you can use it if you would like.
Thank you for any info you could give.
Signature: Jo

Giant Diving Beetle

Dear Jo,
This is a Predaceous Diving Beetle in the genus Dytiscus, and it is an aquatic species that can also fly from one watery environment to another, so finding it on the water catchment barrel makes perfect sense.  At first we thought it must be the Giant Green Water Beetle,
Dytiscus marginicollis, but that species is only reported from the far west, and according to BugGuide:  “posterior yellow band of pronotum broad especially in the middle” and your individual is lacking that band.  Based on this BugGuide image, we now suspect it might be Dytiscus carolinus, though other images of the species show strong grooves in the elytra.  It is described on BugGuide as being “Abdominal sterna colouration reddish to black and elytra with no yellow subapical transverse fascia.”  But for the coloration, that description does fit.  This FlickR image also resembles your individual.  So though we cannot commit to a species, we are confident that this is a Predaceous Diving Beetle in the genus Dytiscus.  Perhaps mardikavana who frequently writes in with identifications might be able to provide a species identification, however we have a previous comment from mardikavana that states:  “I can’t definitely ID it because when you are dealing with dytiscus sp. you need to see the underside as well. “

Correction:  May 14, 2017
Thanks to a comment from Zach Bruder, we learned this is a Giant Diving Beetle,
Cybister fimbriolatus, and according to BugGuide:  “Similar to Dytiscus, but metatarsal claws different. Elytra and pronotum smooth in male. Dilated male protarsus differs in details from that of Dytiscus. Female Cybister has fine furrows on pronotum.”  Here is a BugGuide image of a greenish individual.

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Location: Terlingua Ranch, West Texas

4 Responses to Giant Diving Beetle

  1. zach bruder says:

    That is definitely a Cybister Fimbriolatus. 100%

  2. zach bruder says:

    If you find another, I’d be willing to pay you for it and to ship it out to me. 🙂

  3. zach bruder says:

    People use to call me the bug boy.

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