Not long after we moved to Tucson, my next-door neighbor told me about one of the scourges of our desert gardens: Leaf cutter ants! As their name suggests, they specialize in cutting leaves from plants, and sometimes they can defoliate an entire bush or tree. So when I found some of them living in our gravel driveway, and figured out they were targeting a bush I especially liked for its pretty flowers, I struck back. I killed them.
Now there is a new ant nest. But I’ve learned more about the ants, and I think maybe I won’t kill them because…they are farmers!
The ants cultivate fungus gardens deep under the ground. They feed the fungus freshly cut leaves and can even figure out how the fungus repsonds to different plant material so that they can be sure to bring it lots of what helps it grow best. Currently the fungus garden growing deep under my driveway is being fed mesquite leaves and dried blossoms from my Texas Ranger bushes that recently flowered. The ants walk in long lines to and from the leaf and blossom supply areas, piling material at the doorway to their home, and then work together to haul it all in bit by bit. Then, just like farmers, they have to protect their gardens, in this case from other fungus and molds that would kill their crops. They are helped in their work by a bacterium that grows on their bodies, and that secretes an antimicrobial material helpful to the fungus. Larvae are fed the fungus, and adults live off leaf sap. The fungus needs the ants to stay alive and the larvae need the fungus to stay alive, resulting in what scientists call an “obligatory mutualistic relationship.” In fact, when a Queen heads out to form a new colony, she takes some of the fungus with her to get the new garden started.
The ants don’t like the heat any more than the rest of us, so they hang out in their house all day long, and when temperatures cool at night, or after a good monsoon rain, they come out and get to work. That’s why around here you sometimes see people out at night with their flashlights looking for the lines of ants and their homes. Then the poison comes out and the ants and people fight.
I’m taking a slightly different tack. We have mesquite limbs that are in the wrong place, so as I trim them, I leave small branches at the ants’ door. I figure they can eat what I don’t want, and maybe then they’ll leave some of the stuff I do like alone. So far so good. But who knows what will happen down the road. I’ll let you know.
In the meantime, thanks for farming and ranching and putting food on our tables! We hope that On Pasture is like the mesquite limbs I’m leaving at the ants’ door – just what you need to keep on being successful.
Kathy and Rachel