A green and gold scarab?
Location:  Shelby, MT
September 6, 2010 5:51 pm
Dear Bugman,
I live in Montana and recently found this bug crawling across my dog. *ick*
Upon closer examination the insect seemed to be iridescent with a green and gold color…with a little gold V on his head.
Please I would absolutely love to know what this is….
Signature:  Melissa

Predaceous Diving Beetle

Hi Melissa,
This is a Predaceous Diving Beetle in the genus
Dysticus, and we wonder if perhaps your dog was swimming in a pond just prior to your discovery.  We believe this may by Dysticus dauricus, which we located on the Entomology Collection website of the E.H. Strickland Entomological Museum of the Department of Biological Sciences at the University of AlbertaThe Entomology Collection website describes it as:  “Large (29.7 to 40.0mm), broadly elongate (Larson et al. 2000). Black – some with green appearance. Basal antennal segments yellow, darker and reddish terminal segments. All pronotal margins bordered with yellow. Females with reddish or brown-black striae and black ridges. Reddish yellow or reddish ventral surface, except red metacoxa, medially brown-black metasternum, and black anterior and posterior margins of abdominal sterna. Brown-black or black sternal basolateral maculation – progressively smaller to posterior. Yellow or reddish legs. Interestingly, we overlooked this species when we were searching BugGuide because the photos there look quite different than the photo on the Entomology Collection website.  The Giant Green Diving Beetle, Dytiscus marginicollis, on BugGuide just didn’t seem right. BugGuide does indicate that Dysticus dauricus is “the largest North American dytiscid.” The Entomology Collection website also has this fascinating information of the diet of Dysticus dauricus:  “Predatory – active swimmers (Larson et al. 2000). Invertebrate and fish larvae prey. Records of larval cannibalism and predation on salamanders and snakes in Arizona (Holomuzki 1985, 1986).”  Perhaps Mardikavana can confirm our identification.

Thank You so very much. He was actually not swimming but we have had quiet a bit of rain and I think maybe somehow when I took the dogs outside (both English Mastiffs) he attached himself somewhere out there. Once again…thank you. I spent hours trying to place him.

One Response to Predaceous Diving Beetle

  1. mardikavana says:

    I can’t definitely ID it because when you are dealing with dytiscus sp. you need to see the underside as well. But I can say that this is a female and a rarer version because females usually have furrows on their elyctra.

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