Thursday, August 11, 2011

Learning from Carpenter Ants

Carpenter Ant Colony in a Bounce House
In honor of my biology professor, Adrian Smith, who has devoted his career to studying ants, I chose to learn a little bit about the carpenter ants which until this morning and without my knowledge had built a small colony in my kid's rolled up bounce house.

I have no idea why a colony of carpenter ants would chose to build a satellite community in a rolled up bit of plastic fabric.  It must have been dark and slightly damp and that must have been enough.  It was a poor choice on her behalf.  After the destruction of their nest, the ants were obviously very erratic and grabbed their rice shaped pupae, or egg sacks, and scattered in the grass.  I watched them for a while, trying to determine if they had any idea where they were going, but they just seemed to be running for cover.  Within minutes, each and every egg sack had been picked up and was being carried by an ant in its pincers and within a few minutes, very few pupae were visible.  Ants in general are very good at concealing themselves to avoid predation, so it is difficult to follow ants in grass and see where they go.

They have a colony structure similar to other ants where a mated queen searches for a new home (my rolled up bouncer) and lays eggs that are both workers and queens.  Unmated queens can produce only males.  Carpenter ants do not actually eat wood.  They can't eat solid food because their esophagus is too long and narrow.  So, they gather aphid honeydew and tree sap and they love human food, which is probably what drew them to the bounce house.  They still damage wood, however, by hollowing it out to create their nests, hence their name.  They also have a symbiotic bacteria that biosynthesizes amino acids and other nutrients and plays some role in its nutrition.

I captured one ant and one egg sack during the scattering and used it to identify the ants as carpenter ants by its bent antennae and the shape of the pupae. The confined ant moves in an interesting way, using its antennae to feel around and its two front legs to try and dig through the plastic container I had placed it in.  The other back four legs are spread out to stabilize its movement.  I did see the ant pick up two of its four back side legs and shake them while upside down with only two side legs to hold it in place - impressive acrobatics.  The confined ant is very protective of the pupae and when it isn't carrying it around, it is resting on top of it protectively.  My research indicated that worker ants are required for the new adults to emerge from the pupae - they can't do it on their own.  And for that reason the mother in me can't let the ant die in captivity.  As much as I'd like to keep an example of this ant, I'm going to have to let it go.  I don't want an ant farm in my house and I can't be responsible for its death.  Amazing creatures - as long as they stay out of my house and it's wood.

More photos here.

Gardening in Western Washington

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