Leaf-cutter ants

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It’s been a few days since I’ve posted a blog on here and there’s been so many things I’ve seen in Ecuador alone that I could write about.  I’m in New York now but I have some posts about Ecuador that I still want to put up in the coming weeks or months.  Today I’m going to talk about leaf cutter ants, one of the most interesting social insects I know of.

Leaf-cutter ants are special not just in themselves but in their interactions with their environment (their ecology) and how this has affected their evolution and how they’ve affected the evolution of other organisms.

Sure leaf-cutters live in massive colonies that can be as deep as 10 feet from top to bottom.  They also have trail systems maintained by a special caste of ant.  The trails are actually very well maintained and easy to see snaking through the forest.  Sometimes the trails are really routes, often taking advantage of natural or man-made features (such as the barb-wire fence in the top picture).  There are also soldier castes containing vicious ants with enormous jaws ready to defend queen and colony.

What’s really cool about the ants though, has to do with their namesake, with leaf cutting.  Counter to common perception, the ants don’t eat leaves.  The leaves are actually used as a medium for growing a fungus (think mushroom farm) that they eat.  Leaf-cutter ants are not hunter-gatherers as it would seem but actually farmers.  What’s even more amazing is that the fungus they grow isn’t even found in the wild.  The fungus in the same genus as common grocery store mushrooms (Agaricus bisporus) has such an intimate evolutionary relationship with the ants that it’s dependent on them completely.  The ants grow the fungus underground in temperature controlled chambers, catalyzing the breakdown of leaves with their saliva.  Queen ants carry the spores in buccal pouches and create a garden as soon as they start a new ant colony.

Further the ants can detect fungicides on plant leaves and only collect leaves from trees suitable for the culture of fungi.  If the ants haven’t encountered a tree before and are unsure of it’s suitability they experiment with a small part of the leaf before introducing it en mass to the garden/farm.  The fungi gardens are cleaned, maintained and harvested in a similar way to human farms and the ants are as dependent on their agricultural system as we are on ours.  Below is a youtube video I made of the ants I saw along a road near Mindo, Ecuador.

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