Farmer Ants

So this is why I love ecology.  Just looking at one organism at a time is often super interesting stuff...I mean have you seen a horseshoe crab???  But often the combinations of organisms that have evolved side by side over millions of years is just downright mind-boggling.

I already was a big fan of ants.  I always find it really interesting to watch them and think about how much of their sensory world involves chemicals, many of which are produced by other members of their species.  Ants leave chemical footprints and generally have a few different chemicals that can mean different things.  Their antennae are incredibly acute chemical sensors, able to pick up very small amounts of molecule.

I also knew that ants sometimes farm aphids but after shooting this process the other day I found that these two facts are connected.  I was unable to access the original article here from science daily but I managed to find a quotation of it here.

Scientists have just recently learned that ants that farm aphids, like the ones below, use a chemical produced by their legs to sedate the aphids they are farming.  Ants will often bite the wings off aphids to keep them from flying away and now we know they're also drugging them.  This seems cruel, from a human perspective, but keep in mind that the generally much larger and more capable ants are also defending the aphids from dangerous predators like ladybugs and other beetles.  It's actually rather like our relationship with livestock.  We mess with their genes and keep them corralled but we also protect them from wolves and mountain lions.

These ant colonies keep aphids because aphids produce a sweet liquid known as honeydew as waste when they feed on certain plants.  And the ants...well they consume the aphid waste.  Yum!

The methodology used to discover this is elegantly simple and ingenious.  They had ants walk on a surface and then placed aphids on both a surface that had and had not been walked on by the ants and watched and recorded speeds and such.  They found that surfaces that had been walked on by ants caused the aphids to slow down markedly.  Especially interesting was when they used a dead leaf as a surface.  Aphids should avoid dead leaves at all costs, it's going to make you more obvious to predators and there's no food there for you.  But when they had dead leaves walked on by ants the aphids kind of moseyed off.  Really cool science, I think.

Oh and here are the images.  The little gray blobs are aphids...easier to see in the web album.