A suspicious Prenolepis

Alex Wild
Department of Entomology
University of California, Davis
Davis, CA 95616
e-mail: alwild@ucdavis.edu

     There are only two types of ants in the world: amazing way-cool gee-whiz ants, and small brown things. There's no use kidding ourselves about being enlightened, even-handed intellectuals here. How many of us would fill our last vial with Tapinoma, when the same rock also reveals a colony of Pyramica? Part of the yin and yang of myrmecology is that for every trap-jawed Acanthognathus there is a boring Brachymyrmex, for every spine-encrusted Cephalotes a suffocatingly common Solenopsis.

     I am happy to report an excuse to rescue one of our small brown things from the stifling depths of mediocrity. Prenolepis is one of those ants at which most of us in North America don't look twice. In addition to being small and brown, it is also predictably common. Distressingly, when the even more brown, more small, and monolithically boring Argentine ants invaded urban California, many of our best gee-whiz ants like Pogonomyrmex and Neivamyrmex vanished, leaving us to entertain ourselves with only Prenolepis (and Tetramorium caespitum, of course, as if they were any more interesting...)

      One morning last October I was up in the Sierra Nevada foothills near Nevada City. The anting in early fall in the foothills also tends to be brown and boring, as everything has been baked dry from the California sun and five months without rain. Nonetheless, along the roadside at a scenic viewpoint I was surprised to see a few small alate queens flying low over the ground and clumsily through the low vegetation. They reminded me of little Formica microgyna-group queens, and I stuck a couple in a vial.

      I had a bit of a start when I pulled the queens out of the vial back at the lab. These ants were not Formica at all, but something oddly familiar-looking: Prenolepis. All the more surprising was that these queens were not P. imparis, the only described North American species. They were smaller, with a proportionally smaller abdomen and a noticeably reduced pilosity. Not only that, but imparis flies in the spring, and this was fall. Have we got a second species of Prenolepis in our midst? And judging from the small size and odd phenology, might this be an inquiline? Further tidbits: these queens are locally sympatric with Prenolepis imparis, and we don't have any suspiciously different Prenolepis workers in the Davis collection that would suggest the presence of a second free-living species.

      In the hopes of stirring up some more information on this ant, I have included a photo of one of the queens next to an imparis queen. If any intrepid "Notes" readers have insights on these queens, or have seen something similar, I'd be really interested to hear about it. Surprisingly interested, you might say, considering the small-ness and brown-ness of these ants.

Prenolepis imparis (left) from Davis, CA, and Prenolepis sp. from 5k ENE Nevada City, CA.