Water Scorpion

2012 May 19

On April 22, 2012 we all went to see what we could find at a small pond in the woods behind our house. At one point, Sam took our insect net and randomly swept it through a weedy patch near the shore, and asked me to look to see what was in it. There was a lot of dead plant debris caught in the net, so I reached in to pull it out – and saw that some of it wasn’t dead grass at all.

Well, this was pretty neat! It’s a water scorpion, a more elongated relative of the giant water bug. How elongated was it? It looks to be about three and a half inches, if one includes the very long breathing tubes on the end of its abdomen.

It was very slow-moving and looked pretty fragile, and once we got it out of the water and onto a piece of paper it didn’t seem to be able to lift itself up, so it just lay there[1]

While it was out of the water, it just held its front grabbing claws straight out in front. This may have been because it was more interested in pretending to be a stick than in catching anything to eat at that point.

The underside is pretty similar to the giant water bug underside, if one were to take the giant water bug and stretch it out.

Here’s the giant water bug underside again, for comparison:

Once we put it back in the water, it resumed a more spread-out stance, and started flexing its grasping claws again.

The grasping claws are kind of like a switchblade, and look very useful for grabbing soft-bodied prey like tadpoles[2].

So, this is one of the water scorpions in the genus Ranatra, which are the really elongated ones (there is a second genus of water scorpions that is wider and not as long). Judging from appearance and the range maps, the most likely species appears to be the Brown Water Scorpion, Ranatra fusca. There are a bunch of other species, but those appear to live further south than here.

[1] It turns out that it was able to stand up in the open after all, it’s just that it couldn’t get a grip on a dry sheet of paper with its feet. When I put it into the container to take it back to the pond to release, the plastic was wet enough that its feet would stick, and then it was able to hoist itself to its feet and stand.

[2] Tadpoles are likely a big part of its diet in the pond where we found it, because it was absolutely alive with small frogs and tadpoles. We have a lot of tree frogs and spring peepers around here, to the point where their singing around this pond was absolutely deafening. When we approached the pond, the surface looked like it was boiling from all the tiny frogs jumping in the water. And when Sandy swept the net through the water, it was full of tadpoles.

3 Responses
  1. Bridget permalink
    May 23, 2012

    I want to find one of these now.

  2. May 23, 2012

    Yes, I’m not sure if we found this because we were fantastically lucky, or because the little pond is absolutely crawling with them. We should probably do some systematic sweeping with a net to find out.

  3. Wastrel permalink
    June 12, 2016

    I have only seen this creature, or one like it, one time. It was on the University of Texas campus when they had neglected to clean Littlefield Fountain for several months, and there was an amazing diversity of aquatic insects in it. (They do not put fish in it.) The one I saw was probably 4 or 5 inches long.

    There were also giant water bugs, water boatmen, backswimmers and probably many other insects. I was a graduate student in the Zoology Department at the time and was very excited, but by the time I told some friends and we got back there, they were cleaning the fountain.

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