My first encounter

Photograph by R.H. Scheffrahn, University of Florida

I had known about this ant of course.

Ever since I was perhaps sixteen I had read about its status as an exotic species, one which had profoundly negative effects on native populations of animals and plants.

And yet I did not get to see them first hand until the late 1980s, when I visited the island of Kauai in Hawaii. I wrote this in a journal during my stay there:

This Pheidole species dominates the local ant fauna and seems to thrive almost anywhere: from the sandy beaches near our resort, to the rugged, stony sides of the island's mountains.

The major workers are extremely pugnacious, and the minors only a bit less so. The majors do not feed at mayonnaise baits, but rather move randomly around them, occasionally rushing threateningly at passing minor workers.

The introduction of a formicine ant into a congregation of minor workers at a bait elicited an immediate response. The intruding ant was quickly immobilized by the minor workers, who bit and held onto its legs and antennae. Some two minutes later, a relatively large number of major workers rushed into the scene and started moving all around the place.

This Pheidole is one of the most aggressive extirpators that I have seen. However, due to their relatively small size, they are sometimes not very efficient at acquiring moving "baits".

For example, the black formicines were very quickly and efficiently dragging a large dead wasp to their nest. I took the wasp by the wings and dropped it near some P. megacephala ants, and the formicines immediately began dragging the wasp away again, even before the Pheidole could react. I did this a couple of times more, and at last some minors managed to grab good holds on the wasp legs and prevented the formicines from dragging it away.

The minors were incredibly aggressive, given the fact that they were only a third the size of the very much faster formicine. They grabbed onto the appendages of the black ants whenever the opportunity arose, and let go only when squirted with formic acid. And since the P. megacephala ants are very efficient mass recruiters, the flood of workers that soon followed effectively drove the formicines away.

In order to do justice to the black ants, I placed gobs of mayonnaise near their home nest, at the base of a large pot, about 1 meter away from the scene of the first tussle. The bait was soon covered with black ants.

Just before I left, I noticed a single P. megacephala scout near the black ants' home, and when I came back 20 minutes later, the Pheidole ants had claimed all the mayonnaise gobs near the black ants' nest. Major workers were moving all around the baits as well.