I was walking along a trail in Arizona’s Santa Rita Mountains in August of 2004. It was a beautifully sunny day, and I was out anting. This trail led to a stream that I was interested in exploring, so I was in ‘travel mode’ – focused more on where I wanted to go than where I actually was.
I walked by an old gnarled oak tree that was next to the trail. It had little sparks of gold moving around on it. The effect was quite striking. I looked closer, and saw that the ‘sparks’ were ants. The light was hitting them ‘just so’, and they shone so brightly against the bark of the tree that they seemed to glow.
Ah – this was a colony of Pseudomyrmex apache!
I’d wanted to see these for quite some time. They are unusual-looking ants. They’re very elongate, and have a very wasp-like appearance.
One of their relatives – Pseudomyrmex ferruginea – is famous for their obligate relationship with the Swollen-thorn Acacia. P. ferruginea lives in the hollow bases of specially shaped thorns on these trees, and the tree also grows special protein-rich packets of food (‘Beltian bodies’) for the ants. In return, the ants defend the tree against herbivores – and even vines which attempt to grow on the Acacia.
Pseudomyrmex apache does not have this same relationship with its nest trees. According to what I’ve read, P. apache primarily relies upon old beetle-bored cavities in the tree wood.
According to PS Ward (1985), the sometimes live in distributed nests – so the colony may be spread out spatially in their host tree(s?). Some colonies have multiple queens.
Preserved Pseudomyrmex apache worker on millimeter rule
I’m amazed at how little published information I was able to find on the general biology of these neat little creatures. Seems that’s true of a lot of creatures, especially insects.
I’ve found these ants in the Santa Rita Mountains, and also in the Mazatzal Mountains. Each time, they have been a pleasant surprise.
Sources:
The Antweb.org Pseudomyrmex apache page
The Project Noah Pseudomyrmex page
Ward, Philip S. (1985). The Nearctic Species of the Genus Pseudomyrmex (Hymenoptera: Formicidae). Quaestiones Entomologicae 21: 209-246.
