Ant-Mimic Jumping Spider

2008 May 24

While coming up the hill on my way home from work[1], I spotted what looked, at first, like a medium-sized ant. It didn’t look quite right, though, so I caught it and brought it home. It turned out to be this:

Ant mimic, full body view

It’s a jumping spider that mimics an ant[2]. It’s about the size of the Formica ants we have around here and looks a lot like them. The mimicry extended to its behavior, too. While I was catching it, it pointed its abdomen at me in a threatening sort of way. This is the same pose the ants take when they are annoyed, just before they spray formic acid. So, any predator that had a previous run-in with a Formica ant is likely to assume it’s about to suddenly get another facefull of acid, and beat a retreat. The mimicry is a nice, neat solution to predation for the spider, that works OK for as long as the ants are a lot more common than the spiders.

You can see how much the abdomen looks like the abdomen of an ant here. It even has white lines across it to simulate a segmented abdomen, because ant abdomens are visibly segmented but spider abdomens aren’t:

Ant mimic abdomen

The coloration is pretty similar to the Formica ants, with a black abdomen and the rest of the body dark red. The mimicry falls apart at the head end, which doesn’t look all that ant-like, but that probably doesn’t matter so much. An attacking predator is going to be confronted by the abdomen, and probably won’t even see the head.



I wanted to get some pictures of the face so we could see the eyes, but like a lot of spiders it has the annoying habit of scrunching down with its legs arched over the face. It didn’t want to move, so I tried nudging it a bit with a toothpick to get it to reposition the legs. Unfortunately, this prompted it to suddenly leap out of the dish, dash across the table, and leap off into the nearby bookshelves. It got away clean, after I’d only gotten five pictures. Normally, I have to take about 20 to 40 pictures to get a few that show the details I want to see, so I didn’t get anywhere near as many as I would have liked this time. Without pictures of the eyes, it’s only a guess that it is an “antlike jumping spider”, subfamily Synagelinae. On the plus side, it did confirm that it had pretty substantial jumping abilities, so some species of jumping spider seems pretty likely.

I gather that there are two reasons for spiders to mimic ants. The obvious one is to convince predators that can’t really deal with ants that they won’t be able to deal with the spiders, either, and so leave them alone. The other reason is a bit more insidious: if the ants buy the mimicry, then the spider can sneak up on unsuspecting ants and pounce on them while the ant thinks that they are another nestmate. This usually requires that the spider also emit some scent cues so that they will “smell right”. If it does this well enough, it might even be able to sneak into the nest and feast heartily. I don’t know if this one is a good enough mimic to fool the ants, though. It might just be getting by with giving predators the idea that it’s more dangerous than it actually is, and leaving the ants alone. I’ll have to seriously watch some of our Formica nests to see if there are any ant-mimic spiders hanging around them.

[1] I bicycle to and from work once the show melts, but the last half-mile to our house is really steep (it’s one of those hills that has signs saying “Trucks Use Low Gear”, and I think it’s a 12% grade in some spots). I can ride the bike up the hill, but it wipes me out. So, I push it up, which means I am walking slowly up the hill leaning forward, and can easily scan the paved shoulder to look for interesting critters.

[2] Although, as ant-mimic spiders go, this one isn’t anywhere near as impressive as some others. The one that gets me is this one, where the male spiders actually have turned their mouthparts into a second fake ant, so they are mimicking an ant carrying another ant.

3 Responses
  1. April 9, 2009

    Хм… даже такое бывает.

  2. Shadiac permalink
    April 17, 2009

    Hmmm… If this really is an ant-mimic jumping spider, its mimicry is really lame. I mean, of course, compared to something like this – (which, by the way, also comes from Salticidae).

    And like you said it, those can be quite the defilers of any ants’ nest that they find. Because in theory, the males establishes itself inside an anthill, so that he becomes “part of the gang”. Then he quits the nest and goes around looking for a female to mate with, and finally the female carries its eggsac back to the hill through unsuspecting ants. When the young hatch, they are welcome to join a good feast and can even attack the queen, which is lethal for any colony, of course.

    Also wanted to point out their resseblance to ants. While the abdomen of these spiders is segmented so that it matches those of ants in shape and size, they also use their first pair of legs to imitate ant antennae, waving them up in the air. However, on normal approach, when they are not hunting near to anthills, they do not use their first legs as such, normally using them for motricity. As any Salticidae, they can, of all evidence, jump like crazy. However they can also walk a lot like walking ants do and even stay up like an ant for hours in order to get their prey.

    When bothered by predators, they will keep their ant behaviour until last resort. For example, they will point out the abdomen, or start running rampart like ants do, or even wave around with their “antennae” as if they were about to bite. This behaviour is very contrary to those of other, non-mimicking Salticidae, who simply curl up in a bowl or try to jump away. Only in case of extreme anxiety will it finally abandon its mimicry and make a defensive pose innate to spiders, by putting its thorax up with the first two pair of legs, and kind of hiss (but you won’t hear it anyway). Fascinating, ain’t it? =)

    But of all this, what I really like about jumping ant mimics is their strategy of attack, which must have developed with ages of observation and comprehension of ant behaviour. For example, you all know well that ants carry each other over distances when one of them is either wounded to the point of not being able to run away, or simply dead. They would take this ant with their mandibles and possibly carry it into their lair for “first treatment”. Spiders do the same thing, but in opposite order. When being given the opportunity, it will jump and bite the unsuspecting ant until it’s paralyzed good, sometime even giving it a lethal blow to the head. Then it will take it with its pedipals and carry it away from the anthill in a manner that an ant would carry their wounded. Only once it is far out of reach and unseen by the others, will it finally have another bite and feast on its well-deserved prey.

  3. December 16, 2013

    IMHO this is not a jumping spider. Maybe Gnaphosid ( something like Micaria) or Corinnid, but not a Salticid.

Comments are closed.