Giant Black Water Beetle

bugman

July 24th, 2009 at 2:03 pm

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Shiny Olive-green 3-inch…Beetle?
July 23, 2009
I did not kill this bug!! He was lying on our bumper when we got out of our car at the New York Aquarium in Brooklyn, New York (right by the water on Coney Island). We had driven up from the Washington, DC, area that day and I’m not sure how long he was on board. He was about three inches long and a shiny olive color. If you could just get me started I’m sure I could find him, but all my searches turn up metallic looking bugs, which he was not. Thanks you!!
Hawke
Brooklyn, NY, USA

Giant Black Water Beetle

Hi Hawke,
This is some species of Water Beetle, either a Water Scavenger in the family Hydrophilidae, or a Predaceous Diving Beetle in the family Dytiscidae. According to BugGuide: “Water scavengers have keeled sternum, come up for air head first. Diving beetles have unkeeled sternum, come up for air tail first.” We are inclined to ID this as the Water Scavenger, Hydrophilus triangularis, which BugGuide describes as: “Large, shiny black with olive tinge. Underside with prominent spine (prosternal process). Similar to the usually smaller H. (Dibolocelus) ovatus. H. triangluaris is more oblong, H. ovatus more oval. H. ovatus is more common southward.” The common name is the Giant Black Water Beetle.

Confirmation from Eric Eaton
Daniel:
The giant black water beetle is indeed Hydrophilus triangularis.
Eric

Found this picture http://davesgarden.com/guides/bf/showimage/5301/ which sure looks like him.
Thanks! I was stumped.
My husband says he saved him to put by the computer… if he is intact I’ll try to take a better picture. He was quite an impressive creature and I didn’t see any others on What’s That Bug.
Thanks!
Hawke