Mimicry again – ant-spider

Small red and black insect
Ant? No, spider – Jumping Spider, in fact

A few days ago I showed a fly pretending to be a wasp (at bottom of previous post). On almost the same day I saw a little insect 5-6 mm long scurrying around on the broad strap-like leaf of a lily. It looked like an ant, but somehow not quite right. The camera let me stop it and magnify it, and see that it was in fact a spider.

Merely counting  the legs is enough to make that judgement, but we can go further. Looking at the eye pattern (you may need to click on the image to see the detail) puts it into the large family of Jumping Spiders, Salticidae. As roaming hunters, salticids depend totally on good eyesight and their upper central eyes are very large and face forward.

I was quite puzzled the first time I saw one (the one below), almost exactly a year ago: the body is very ant-like and the front end is … bizarre. We expect spiders to have two distinct sections, head (technically ‘cephalothorax’) and body (abdomen) but this one seems to be in three sections, with two fat rods sticking out in front of the head – as big as the head, too. They are actually its jaws, enormously enlarged to give it more of a three-part ant profile.

black ant-mimicking spider
Another ant-mimicking Jumping Spider

I haven’t been able to completely identify either of these two. I am fairly confident they are Myrmarachne species but haven’t found any just like them on the web. I don’t feel too guilty about that because there are nearly 80 described species, and more to come, according to the experts. There’s a user-friendly introduction to them here, on the excellent Brisbane Insects site, and some of the species are described¬† here, on Arachne.org (scroll down to Myrmarachne – but detour to Maratus if you want a treat).

7 thoughts on “Mimicry again – ant-spider”

  1. I’d have a guess at the top one being a male Myrmarachne rubra according to (Ceccarelli, 2010 – New species of ant-mimicking jumping spiders of the genus Myrmarachne MacLeay, 1839 (Araneae: Salticidae) from north Queensland, Australia). That’s probably true for the 2nd as well. They mimic red strobe ants (Opisthopsis) and the jaws of the males are thought to be compound mimicry of an ant carrying something. Amazing really.

  2. I live in north east Ohio and I found one of these spiders in my bathroom earlier today. I thought it was a spider but wasn’t sure. Thanks for the info.

  3. I saw a very similar spider the other day. I live just north of Byron Bay. It was all black, looked very much like an ant but had these bizarre rod like ‘mandibles’ like this. I know it wasn’t quite right for an ant, too, and on closer inspection saw that it had 8 legs and was using the front two in a way that made them look like antennae. Thanks for the post :)

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