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1

Júlio came up with the correct answer to the questions in the last post.

Species 5 is Acromyrmex versicolor, and this worker was carrying a very large piece of caterpillar frass. As I noted in the comment, the frass is most likely from a Manduca rustica caterpillar, as there was a host tree nearby.

(I apologize for the quality of the photograph. I was lying flat on my stomach on the sidewalk in a very public place while this ant was moving rapidly along.)

Júlio also wondered about an Acromyrmex versicolor worker carrying frass, which is something other leafcutters like Mycocepurus or Cyphomyrmex or even Trachymyrmex are more like to do.

I did locate the nest entrance. The workers were variable in size, showing different castes.

They appeared to have three pairs of spines on the mesosoma.

The workers were definitely collecting plant material. So, I think it is safe to say these ants were Acromyrmex versicolor.

And there's a Dorymyrmex making an appearance.

As for the ant-finding challenge, I thought I did pretty well to find honeypot ants and leafcutters within two hours, but then again it is pretty easy to find cool ants in Tucson.

Summary:

I found a total of eight different ant species, less than the expert at the Tucson airport, but still a lot of fun.

Crematogaster opuntiae

Forelius, probably mccooki

Brachymyrmex patagonicus

Myrmecocystus placodops

Acrimyrmex versicolor

Solenopsis xyloni

Dorymyrmex sp.

plus one species I, gulp, could not identify and the photographs are not a help.

I know I could have found more if I could have flipped rocks or tore into trees, but this was a public place with prohibitions on that sort of thing. Surprisingly, there were no harvester ants in the list. I'm not sure why not, because I find them quite often in other places.

So, what do you think about Acromyrmex carrying caterpillar frass? Is that common behavior or not?

4

The challenge: to see how many species of ants I could find in Tucson, Arizona in two hours.

Species 5:  You tell me.

To make this a little more fun, why don't you tell me what the fifth species is.

Bonus:  What is this ant carrying?

4

The challenge: to see how many species of ants I could find in Tucson, Arizona in two hours.

Species 4. Myrmecocystus placodops

In addition to the usual suspects, Tuscon has quite a few interesting species.

What are those peeking out of a hole?

Taking a closer look, I found worker ants with black bodies, red heads and long antennae.

The workers were milling about at the nest entrance, aware of my presence.

These are Myrmecocystus placodops, a type of honeypot ant.

Honeypot ants are the camels of the ant family. They live in dry areas throughout the world where food and water may be scarce for long periods of time. To cope, honeypot ants have unique storage tanks for holding liquids. These storage tanks are special large individual worker ants called repletes.

When times are good and food is abundant, the repletes store any extra liquid food that is available and swell up like balloons. Then they hang around, literally, from the ceiling of the nest, until times are tough. If the colony runs out of food, the other workers entice the repletes to spit up their reserves to share with the others.

Honeypot ants have deep nests. Mammal predators, such as badgers, are known to dig the nests open in search of the repletes.

Watching these, I had to wonder about the red heads. Remember the stories about the parasitic nematode that causes an ant's gaster to swell up like a red berry to make it enticing to birds (see National Geographic's version)? Looking at those photographs reminded me of a reverse of these ants, which have bright heads instead.

Have you ever encountered Myrmecocystus placodops?
What do you think of those red heads?