Tuesday, September 27, 2011

Velvet Ants and Ant Police

While staying up too late last night and browsing my favorite subreddit,r/whatsthisbug, I came across a picture of a bug I actually recognized, the velvet ant.  Now, the velvet ant is not actually an ant, but a relative of all ants and wasps.  The males have wings and often aren't identified easily, but the females, unusually in wasps and ants, lack wings and have bright red or orange fur covering their bodies.  They are a very cool insect to find, but they are said to have one of the most painful stings in the insect kingdom, so whenever I've seen one here in New Mexico, I've never tried to pick it up.

Now, I'm getting sidetracked here, because what I wanted to really talk about was what happened in the discussion of that velvet ant photo.  I don't often chime in to these discussions, because more knowledgeable scientists and bug trackers are usually around to identify creatures down to the genus or species, when I have more of a layman's understanding of arthropods.  But I had to here, because people started talking about ants and ant egg-laying behavior, and ants, as you will know doubt discover while you're here, are my favorite, and there are few books about ants out there I haven't read.

So, people were asking if worker ants ever laid eggs, and a few bug experts replied, no, only the queen lays eggs, and the question was assumed answered and left at that.  But I, having just read a book called Sex on Six Legs by Marlene Zuk, and having heard of this particular behavior before, knew better.

If there's one thing you know about ants, it's probably that the queen is the only ant in the colony who lays eggs, and all the other ants are workers who serve her.  Well, just like learning that the solar system has eight planets (or nine, in my day), this is another "fact" that turns out only to be half-true.  Scientists have observed worker ants laying eggs.  Even more remarkably, when other workers notice this, they will eat the eggs and, for good measure, beat up the egg-laying worker, pulling on her antennae.  This has been dubbed "policing" behavior.

So what's going on here?  Well, it's crucial here to understand that all biology boils down to genetics, really.  All those little genes in your DNA, in every cell in your body, only got here by reproducing themselves successfully, without a care as to the body or behaviors they were actually shaping.  Genes are selfish.  So anything at all that gets a set of genes passed on to the next generation the living thing will do, whatever it is.  This all happens by itself through trial and error.  The errors are any once-living thing that couldn't pass on its genes and isn't around today.

Now, what chance does a worker ant, who is essentially sterile and can't mate, have to pass on her genes?  We all know the most common strategy:  serve the queen.  The queen gave the worker her genes, but the queen still has those same genes, and the queen is still laying eggs with those genes.  Since the queen's eggs can be reproductive male drones or new queens, and those ants can start a new generation, a worker often best serves her own interests by protecting these eggs and keeping the queen and colony strong.

But there is another, sneakier strategy.  Occasionally, a worker ant's ovaries, her egg-laying internal machinery, will develop and begin producing eggs.  If she lays an egg, and that egg hatches, the baby ant will always be a male drone, fully capable of reproduction with a new queen.  The worker mother wants her own young to succeed, because it is a way for her to pass on her genes directly, and not waste time raising her sisters, who do not share %100 of her genes.  However, her sister workers would be wasting their time raising her drone young, since they do not serve the queen's reproduction, and therefore not their own.  So they remove the problem.  The other workers will eat the rogue worker's eggs and rough her up a bit to teach her a lesson.  Often the worker's ovaries will then shut off and she'll resume the life of a lowly worker.
I could even go into more detail here about each ants' genetic relationships to each other, but I've already written more than I meant to on the subject.  Anyway, the bug expert on Reddit was amazed, as he had never heard of such a behavior.  The papers are out there, though, and can be found with a Google search.  You might try "worker ant policing behavior" for a good number of hits.

Well, that was my first post, and it felt good!  Feel free to leave a comment, or ask a question!

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