Friday, August 15, 2014

An ant? No an ant-mimicking spider!

As a student I wasn't really interested in the small creatures like the arthropods no matter how abundant they were everywhere around me. However, I believed that I knew what an ant is and what a spider is, but nothing much than that. So one day soon after I began my life as an amateur biologist, when my mentor showed me an ant and told me that it's a spider, I wasn't really sure about his identification. But a close examination proved that I was wrong. Indeed there are spiders that look like ants.

Spiders are a divers group of organisms with many different forms and shapes. Among the World's spiders the most abundant group is the Family Salticidae of which the members are commonly referred to as "jumping spiders". Even the jumping spiders are very diverse in their morphology. All these are characterized with two large eyes on the front and a total of eight eyes. Most of the ant-mimicking spiders stands among these jumpers of the Salticidae. The most common of these are found in the Myrmarachne genera which is mainly distributed in the old world even though some members are found in the new world too. In both these regions usually they are more abundant in the tropics. Other than the jumping spiders, there are spiders that mimic ants belonging to other spider families too but usually they are not commonly referred to as ant-mimicking spiders.

The ant-mimicking spiders look similar to an ant in general body colour and shapes. Their cephalothorax appear as two distinct tagma mimicking the head and the thorax of an ant and the first pair of legs are kept lifted in to the air mimicking the antennas of the ants. In size also they are similar to the species of ant they are mimicking. The chelicerae of the ant-mimicking spider males are elongated than that of the females.

However some features makes the distinction of each group from the other easily. A close examination of the antenna looking appendages of the ant mimicking spiders will allow the observer to notice that they are connected to the thorax proving that they are actually legs, not antennas. In many cases that I have observed, the behaviour of these spiders are also different from the ants. It always allowed me to readily identify spiders among ants. Their movements are usually different and they can jump unlike most of the ants. And these spiders can hang from their silky threads, how many ants can achieve that? None.

The reason behind this mimicry is finding protection from the potential predators. As many animals do not prey upon ants due to the formic acid they produce the spiders also can achieve the same protection by mimicking the ants. In some species the spiders use the mimicry to hunt the ants they mimic or to prey upon the aphids that the ants tend to.

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