Small Rove Beetle, Large Fishing Spider

2009 June 13

We’re having a twofer this week, because I have two subjects with only one good photo each, and not enough to say about either one to warrant a full entry

The first is a little guy, about 4 millimeters long, that S_ found scooting across the floor in the living room. It was very like an earwig, with a similar sheen, flexibility, and tendency to squirm out of tiny places. The only thing is, it didn’t have the forceps at the end of the abdomen. Unfortunately, I only managed to take four nearly-identical pictures before it suddenly scooted off and disappeared under my photography stand, so this is the only real picture available:

At first I thought maybe it was an earwig nymph, since I wasn’t sure whether or not earwigs have their forceps all their lives, or only develop them as adults. The folks at Bug Guide soon set me straight, of course: V. Belov quickly identified it as a Rove Beetle in the subfamily Tachyporinae, which for some reason are called “Crab-Like Rove Beetles”. These are minute, mostly-predatory, very un-beetle-like beetles that generally live in the leaf litter and under rocks. They are very common, but not often seen, because they are pretty tiny guys. They have wings tucked under those little pads on the back, but it is evidently quite a project for them to unstow the wings and take flight, so they mostly don’t. I understand there are a few thousand kinds of rove beetles, so we certainly aren’t done with them yet.

The second is a very nice picture of a wolf spider that our friend Michelle took down in Munising last year. While it isn’t technically from our yard, Munising is less than 100 miles away as the crow flies (and maybe 150 by road), so the same species is likely to be around here, too.
At first, I thought it might be the same species as the wolf spider I posted here a few weeks ago, but then I compared them side by side and realized that Michelle’s spider was a dark-colored spider with light stripes on each side, while the the previously-posted one was a light-colored spider with dark stripes on each side; practically a photographic negative of it! Observe:
They otherwise are of comparable size, and probably very similar habits (except, of course, for the fact that Michelle’s was found outdoors, while ours had gotten into the house). Incidentally, we’ve had a chance to watch how our wolf spider catches flies that are nearly as big as he is: when the fly gets within about an inch, he will leap at it, wrapping his legs completely around, and hang on while the fly buzzes and the fly/spider ball rolls around all over the floor of his terrarium. Then he will quickly bite it right in the back of the head, and within a few seconds it’s all over. Very fast[1].

Update: I recently acquired a copy of the book Spiders of the North Woods, and it turns out that Michelle’s spider is not a wolf spider at all. The inverted color scheme is more consistent with it being a Fishing Spider, in the Dolomedes genus. And in the comments below, “B” identified it as a 6-spotted fishing spider, Dolomedes triton. These are large spiders that live near water, and snatch food that gets too close to the surface. The big ones do, in fact, eat small fish when they can catch them. Up until now, I hadn’t realized that fishing spiders lived up here, for some reason I thought they were a southern species.

[1] And, I might add, completely unlike the scenes in either “The Fly” or “The Incredible Shrinking Man”, where the spider slowly menaces its prey over a period of minutes. No, it’s very much a leap-grab-bite-it’s-all-over-now sort of thing. Spiders aren’t into playing with their food. Not like cats.

8 Responses
  1. June 14, 2009

    I’ve noticed that about spiders and food. My Steatoda bipunctata dashes in, bites the prey, then backs off, looks it over for a few seconds, and sets about tying it up.

    I take the lid off her jar, pop in the unfortunate victim, and replace the lid. Often she has her prey immobilized before the lid is tightened down.

  2. June 18, 2009

    Morrissey (the Resident Feline) adopts a similar strategy when it comes to damselflies. V effective. I wish he wasn’t. Thank you for the link, btw.

  3. June 19, 2009

    Great shots and nice post. You should name the beetle “Karl.”

  4. June 20, 2009

    I’ve always thought that wolf spiders looked like particularly cheerful fellows. Well, except for the leaping and wrapping and biting and killing part, that is.

  5. March 31, 2011

    Thank you so much for your information on local Spiders! I am currently constructing a scrapbook page highlighting all of the bugs that my children found one summer. Amongst them, a Fishing Spider, which I have been informed of many times, was a Wood Spider, and commonly a Wolf Spider. Love the info and links, thanks a bunch for helping me get the facts correct for my childrens learning.

  6. April 1, 2011

    You’re welcome. I really need to find another fishing spider for photographs, I’d like to get some better shots of the eyes. We almost caught one down by Otter Lake last spring, but it was too quick for us.

  7. September 6, 2011

    The middle one is a 6 spotted fishing spider. 100% on it

  8. September 7, 2011

    Thanks for the confirmation, B. Now I really want to find one myself, so that I can get more than one photograph.

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