I’d like to start this post off with a picture:
It’s an ant. A weaver ant to be precise, found in India and China. It’s a pretty mundane looking ant, so why am I blogging about it? Well, lets look a little bit more closely at the picture. Okay, six legs, big antenna, big eyes, three body sections, large pincers. All very ant-like. But not quite. Let’s look even closer. Those two large antennae aren’t really coming out of the ant’s head, are they? No, they look suspiciously like they emerge from the ant’s body. So maybe they’re… legs? But ants have six legs, don’t they? Well let’s leave that for the moment and look at those big eyes. If you look a bit closer at the front of the ant’s head, there seem to be more eyes that face forward. There are eight of them, in fact. Okay… eight legs, eight eyes… not very ant-like. Because this ‘ant’ isn’t an ant at all. It’s a jumping spider. A Kerengga ant-like jumper to be exact. This is what the actual weaver ant looks like:
Not a bad imitation, right? When I first came across the ant-like jumper the similarity just blew my mind. Upon conducting further research it became clear that this mimicry isn’t unique to this one spider. The entire genus Myrmarachne (which translates to ‘ant spider’), to which the Kerengga jumper belongs, uses this technique. Ant mimicry is actually fairly common, and is seen in different families of spiders, beetles, mites and other insects. Ants are popular among mimics because most either taste bad or are very aggressive, so predators avoid them. Another, sneakier reason for mimicry is that certain mimics (not the Kerengga spider) disguise themselves as ants so they can hunt them more easily.
Many of these mimics have the act down to an art. The Kerengga ant-like jumper moves exactly like the weaver ant; it even waves it’s front legs in the air like antennae. Spiders have only two body segments, the cephalothorax and the abdomen. To imitate the ant’s three body sections, constrictions on the spider’s two segments creat a false thorax and head from the cephalothorax, while the abdomen is constricted to create a long slender waist that resembles the weaver ant’s.
While this sort of dedicated imitation is nothing short of amazing, this is only half the story of the Kerengga ant-like jumper. You see, that picture is of a female spider. The males look quite different. Many male jumping spiders compete for mates, something that in nature leads to sexual dimorphism, where the two sexes look very different. In the Kerengga spider, males compete for females using long jaws, which can be up to one-third their body length. The jaws can open up, and two males will stand off against one another, jaws spread wide. Usually the male with the larger jawspan is the winner, and the other spider will back down. If neither male backs down, a fight may ensue, where the two males use their jaws like swords.
When you look at the lengths the spiders have gone to to imitate the weaver ant, these jaws seem very cumbersome and pointless. In fact, they are so large and useless that once they are sexually mature, male Kerengga spiders stop eating altogether. But how can male spiders hide such conspicuous appendages? The solution is quite ingenious.The mimicry isn’t as perfect as that of the female jumping spider, but when their jaws are closed, male spiders look like a weaver ant carrying a small worker ant. Here’s a picture:
Like I said, not perfect, but still a pretty good way of hiding ungainly jaws. From a distance, and maybe even at close range, the Kerengga ant-like jumper would be indistinguishable from the weaver ant. The spiders live close to ant colonies, and this offers excellent protection from predators. Though the animal world is full of excellent mimics, I have to say these spiders have got to be right up there in terms of most successful disguise.
As I final note I would like to say I am very scared of spiders. The way they look, the way they move, just makes me shudder. That being said, spiders are a fascinating and diverse group of animals who have adapted in very different and interesting ways for survival, so expect to see more of them in this blog! But the Kerengga ant-like jumper (and other Myrmarachne) get extra points because they don’t look, or move, like spiders at all. So I guess what I’m trying to say is that this is my new favourite spider.