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<b>Down South, Out West</b><br><i>Sir Bob Harvey’s son Fraser walks New Zealand’s Karekare<br>Photo by Dana Edmunds</i>
Vol. 17, no. 5
October/November 2014


Kingdom of the Ants 
Story By: John Gregg
Photos By: Jack Wolford

It might be hard to imagine now, but there was a time not so long ago when there were no ants in Hawai‘i. Not one. You couldn’t tell by looking around these days; they’re legion. I’ve got at least eight species in my house alone—amber ants with big black heads in the living room, almost-invisible gray ones in the cat food, small black ones gathered around drops of water by the kitchen sink like Bedouins drinking from an oasis. And I’m not alone: Like everyone in Hawai‘i, I live among ants. But I’ve never complained, and I never really paid much attention to them—price of paradise and all that. And I always looked down my nose at the tourists who screech at every roach and gecko scurrying across their path. It’s the tropics, I’d smirk inwardly. There are critters.

We shouldn’t be surprised to find ants in “our” habitats, writes Harvard entomologist E.O. Wilson, probably the best-known ant expert in the world. In his authoritative tome The Ants he writes that ants and termites together comprise about a third of the animal biomass of the Amazon rainforest, “with each hectare of soil containing in excess of eight million ants.” Even in temperate areas, ants dominate. Wilson notes that one super-colony of Formica yessensis in Japan had some 306 million workers, over a million queens and covered a 2.7-square-kilometer area. Those are astonishing numbers; equally astonishing is the diversity. One German entomologist collected 350 species of ants just in the narrow valley of Peru’s Rio Yuyapichis. Wilson himself counted forty-three species in a single tree in the Tambopata Reserve in the Peruvian Amazon.
While ants are the kings of most tropical regions, that wasn’t the case in Hawai‘i. “The only places free of native species,” Wilson writes, “are Antarctica, Iceland, Greenland, Polynesia east of Tonga and a few of the most remote islands in the Atlantic and Indian Oceans.” The fifty-eight or so species of ants known in Hawai‘i today (and the half-dozen in my house) are all introduced—and recently.

One thing you learn quickly about ants is that many species become invasive when they reach a new environment. In fact, Hawai‘i is now home to four of the big five most invasive species in the world: the yellow crazy ant, the Argentine ant, the big-headed ant and the little fire ant. (The only marauder missing is the dreaded RIFA—the red imported fire ant—which is wreaking havoc across the American South.) Seen from that perspective, ants are a major problem. But they’re also pretty awesome, in the true sense of that word. Even the people in the state who are tasked with the Sisyphean job of trying to control them concede a sometimes grudging amazement. Take Paul Krushelnycky, an entomologist at the University of Hawai‘i at Manoa and the Hawai‘i expert on AntWeb, a popular web site for all things ant. As a doctoral student at UC Berkeley and then as a biologist with the US Geological Service, Krushelnycky studied the impact of Argentine ants on Haleakala National Park, specifically whether the ants were affecting the park’s endemic silversword plants. Krushelnycky knows as much as anyone about ants that have made a home in Hawai‘i, which is a great deal but also not as much as you’d think. There’s much we still don’t know about our uninvited guests.

It turns out the black-headed ants marching around my living room are the aptly named big-headed ant, Pheidole megacephala. They typically prefer to be outdoors, so it’s interesting, Krushelnycky says, that they’re in my house. They’re a major pest in almost all low-elevation areas of Hawai‘i, driving out not just the native insects, but other introduced ant species, including Krushelnycky’s own specialty, the Argentine ant. While the big-headed ant prefers a tropical climate, the Argentine ant does best in what might be called a Mediterranean climate like the Central Valley of California, France, Spain, South Africa and parts of Australia. “In Hawai‘i they were first established around Fort Shafter,” says Krushelnycky, “and you could find them in coastal areas.”
That changed, though, with the arrival of the big-headed ants. “Over time the Argentine ants seem to have disappeared from most of the lowland areas,” Krushelnycky says. “I’m not sure if that’s because those areas aren’t suitable climatically or whether they just got out-competed by other ants. In any case, in Hawai‘i, Argentine ants now seem to thrive anywhere from three thousand feet and up.” That’s why they’re a problem on Haleakala and not in my house.