Pheidole tepicana

A century ago, William Morton Wheeler inked this iconic illustration of the striking polymorphism displayed among members of an ant colony. You may have seen it; Andrew Bourke and Nigel Franks used it as the cover for their 1995 text Social Evolution in Ants.

I always assumed Wheeler's figure depicted some exotic tropical marauder ant, a voracious jungle species with massive soldiers for slicing up hapless prey. I don't read captions carefully enough, I guess, because I learned recently that this charismatic creature is actually a local harvester ant, Pheidole tepicana. Not only that, but the lab downstairs from mine keeps several captive colonies for research on caste development. Obligingly, last week they let me stop in with my camera to take some photos.

The largest workers have absolutely massive heads:

A salient fact about Pheidole tepicana- and presumably the reason why Wheeler singled it out- is the extensive variation in shapes and sizes of workers. Most ant colonies are monomorphic; that is, all their workers are roughly the same build. Most of the thousand or so species of the genus Pheidole are impressively dimorphic, with a mix of small normally-proportioned minor workers and a few large-headed major workers. A small subset of Pheidole species take this a step further and have become trimorphic, usually by adding a grotesquely front-heavy supermajor. Here we can see all three morphs:

A major worker with two supermajors:

A minor with a supermajor:

A minor:


A male, with majors and minors:

Hello Mr. Photographer!

More like this

Pheidole creightoni major worker, California After reading a couple times through Corrie Moreau's hot-off-the-press Pheidole evolution paper, I am pleased to give it a thumbs-up. The paper is behind a subscription barrier, so I have distilled the results into an informal summary: Pheidole is…
Pheidole dentata, older worker with larva. A study out in pre-print by Muscedere, Willey, and Traniello in the journal Animal Behaviour finds little support for a long-held idea that worker ants change specializations to perform different types of work as they age.  By creating colonies out of…
Pheidole moerens, major worker, Louisiana Pheidole moerens is a small, barely noticeable insect that travels about with human commerce, arriving without announcement and slipping quietly into the leaf litter and potted plants about town.   As introduced ants go, P. moerens is timid and innocuous…
Neivamyrmex nigrescens, Arizona Army ants have a decidedly tropical reputation.  The term conjures spectacular images of swarms sweeping across remote Amazonian villages, devouring chickens, cows, and small children unlucky enough to find themselves in the path of the ants.  Of course, the…

One of my favorite Pheidole species, Ive only seen it in the field a couple of times. Nice.

By Anonymous (not verified) on 26 Jul 2008 #permalink

Crap did it again forgot who I was.


Well, minor ant is Carebara mayri 0,7 at 1,00 mm, but not photo for probe, life into Amazon jungle, invisible at eye, you need photo for reserach