Wednesday, 3 February 2010

Ants, Spiders and Ant-Spiders

DSC05510.jpg

I was out searching for insects to photograph, when I came across what appeared to be an ant, crawling up a curry leaf tree. However, as I took my first shot I realized that something was grossly wrong with the “ant’s” morphology. It seemed to have jaws that were too big and eyes were too closely spaced on its head. I then noticed that it wasn’t really an ant at all, it was a spider!

DSC05511.jpg

From appearances, the ant-spider resembled the ant species below the most, so I guess it is an imitation of this ant (identification anyone?). These ants are one of the toughest ants I know of and I cant imagine any other insect being able to break through its hard exoskeleton to prey on it (but of course there will always be predators).

DSC05211.jpg

Mimicing ants (myrmecomorphy) is a very common strategy employed by many insects. Spiders commonly do it too and are thought to employ it for two purposes. The most obvious reason being predation -in order to get closer to the ants and feed upon them. DSC05508.jpg

However, spiders have a much better reason to do so – Batesian mimicry.  Ants are mostly unpalatable and are thus avoided by most birds and other insects. Thus if other insects manage to convince predators that they are ants, they may get away without being eaten.

DSC05512.jpg

The curry-leaf tree did not host any of the former ant species and as far as I can say the above imitation is for protection and not predation. What the curry leaf tree did have though, was an entirely different looking species of ants who appeared to be busy feeding/tending to the leaves of the tree. It appears to be tending to miniscule aphids on the leaves.

DSC05526.jpgDSC05530.jpg

These tiny ants were at least 4 times smaller than the spider and thus its unlikely to be the model for the ants mimicry.

DSC05532.jpgDSC05543.jpg

However, there seemed to be a slightly longer type of ant  among the population.

DSC05541.jpg

..and the two types seemed to be getting along well and even sharing their aphids. Perhaps it could be a soldier of the same species (?)

DSC05544.jpg

While these ants were scurrying about, I managed to find one individual that seemed to sit still, munching upon what appeared to be one of the aphids.

DSC05547.jpg

However, as I shifted angles to approach it from the front, I realised that I was fooled again.

DSC05555.jpg

This was no ant…this was another ant-spider!

DSC05558.jpg

This time though, it was clear that the  spider was trying to mimic the longer ants that I have shown above.

DSC05560.jpg

It may not be a perfect imitation but its enough to fool anyone at first glance.

DSC05576.jpg

About 80% of the spiders with Batesian mimicry are thought to imitate ants, so I`m sure I`ll be encountering more of these, so keep watching this space if you are interested.

PS.

My guess is that the first ant-spider is Myrmarachne maxillosa and its model is the Polyharchis species


Share/Save/Bookmark

2 comments:

Post a Comment