Sac Spider, or maybe Ghost Spider

2013 November 27

We were spotting these smallish (less than a quarter-inch long), pale spiders off and on all through the winter of 2013. This particular one was found on an exterior door on a part that was covered by a snowbank on March 2, 2013. It was evidently running around under the snow.

There was also at least one living in our car for most of April, and as the snow started melting we saw them regularly cruising around on our house siding whenever the temperature got above freezing. They evidently are roving hunters, not web-weavers. They were pretty willing to tackle whatever they could, too. While I can’t be absolutely sure it was the same species, I think it was one of these that I saw fly past riding on the back of a midge about twice its size. The pair of them ran into the side of our house, at which point the spider then quickly dragged the midge into a crack in the siding, presumably to finish it off.

I thought they were wolf spiders at first, but the eye pattern isn’t quite right. Wolf spiders have two central eyes that are much bigger than the other eyes, with four eyes underneath and two more around on the sides. This one has all the eyes about the same size, with two central eyes and the other six all running in a close arc across the face.

It looks like it may actually be either a Sac Spider in the family Clubionidae, or possibly a “Ghost Spider” in the family Anyphaenidae. BugGuide gives the distinguishing features between these two families as “[ghost spiders] have two rows of club-shaped hairs on the bottoms of their feet, and their tracheal spiracle is located well in front of the spinnerets, unlike most spiders which have their tracheal opening right in front of the spinnerets.” I don’t think I can see either of these details in my pictures, so we may be out of luck here.

There’s a pretty good chance that this is an immature spider, too. A lot of spiders go through the winter immature, eating the sorts of tiny things that one can find in the leaf litter.

Sac spiders are known for building little silk hideouts, often in curled-up leaves, which they hang out in when not hunting. So if you find a plant with a curled leaf, unroll the leaf, and have a spider suddenly dash out and run up your arm, it may be one of these (although I’ve had the unrelated jumping spiders do the same sort of thing to me).

7 Responses
  1. Katbird permalink
    November 27, 2013

    Have you checked Richard Bradley’s book?

  2. Carole permalink
    November 27, 2013

    Wonderful vision of the midge sailing past with a spider on its back. Sounds like something out of a Animal House. This is a good time to thank you for all the knowledge you’ve shared. Have a good Thanksgiving.

  3. November 27, 2013

    Although the characters we need for a definitive ID aren’t visible, two things really jump out at me: the fuzz on the carapace and the arrangement of nearly six eyes in a row. Both of those are common to the Hibana genus, though not diagnostic for the genus. That doesn’t place this in Hibana, but it does strongly suggest Anyphaenidae.

  4. Bridget permalink
    November 28, 2013

    I was bitten by a yellow sac spider last spring. I actually thought I had been bitten by a brown recluse because the symptoms were so similar but much milder. I was bitten on the elbow twice and once on my hip…the spider was living in the couch I was laying on.

    I still like spiders. I don’t blame the spider for biting me, it was only defending itself.

  5. November 28, 2013

    Glad you still like spiders. They really don’t like being squished, even if by accident.

    Just so you know, there are no verified cases of North American yellow sac spiders causing necrosis ( One thing we do know with certainty is that the moment you are bitten by one of these, you feel it, and it hurts like crazy. Apparently it has one of the more painful spider bites.

  6. Katbird permalink
    November 29, 2013

    Spider Joe- Thanks for the reference. We had heard about these necrotic bites for years. One a few years ago was a famous football player out west. Maybe he had MRSA or something instead.

    The yellow sac spiders are supposed to be more pugnacious that a lot of our native spiders, but who knows?

  7. December 2, 2013

    Katbird: Nope, I don’t have a copy of Bradley’s book yet. Maybe I should get one.

    Spiderjoe: Thanks for the ID information, and the comments about spider bites. I’ve been making the point myself that spider bites aren’t anywhere near as common as people think, and that in spite of harassing a lot of spiders over the years, none of them have ever offered to bite me. Although, that’s probably because spiders are so fragile that I treat them gently, to avoid squashing them or making them shed legs.

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