Whoops there goes another ant attack

Poor beleaguered New Orleans has another mark against it: About 100 years ago it was the U.S. port of entry for the tiny Argentine ants that now rampage through kitchens in Mediterranean climates around the world.

As is often the case for transplanted species, Argentine ants in their native South America are just part of the natural world. But in their adopted homes, they are too successful and become pests. These tiny ants are so successful, and so devastating to native ants, because they can live in colonies that are immense compared to those of other ants.

Some of their supercolonies link thousands of smaller ones and stretch across whole countries. Researchers have noticed a lack of aggression between Argentine ants from linked adjacent colonies, but they don’t agree about exactly what this means and how the ants do it.

The reigning hypothesis is that the Argentine ants wage few wars against adjacent colonies of their own species, so they concentrate their energies on building up their population.

Worldwide, there are about 12,000 ant species. California has fewer than 100 of these. Where Argentine ants invade, the number of native ant species falls drastically.

One of the first to disappear is the red harvester ant. The red harvester ant is fairly common in sandy areas in the park, and they build their nests often on trails.

Colonies are marked by a vast (to an ant) field of litter surrounding the entrance holes. The aptly named harvester ants spread out into the vegetation, harvesting seeds and other edibles. At the nest they further process the food. Rejected bits get dumped outside the nest opening, along with unwanted pebbles from inside the nest.

When the harvester ants disappear, it’s also bad news for wildlife like the threatened San Diego Coast Horned Lizards. They eat primarily red harvester ants, and in lab tests, could not or would not eat Argentine ants.

Argentine ants actually prefer a wetter climate; lack of water prevents them from colonizing the wilderness. They invade through watered fuel modification zones, and stop pretty much at the end of that area. So although our parks are still mostly invader-free, our urban areas are not.

In my garden are either two large colonies, or one giant one. I wage a constant battle with tiny kitchen invaders, putting all the foodstuffs in the pantry in zipper-top plastic bags. Finally, I deployed a super weapon ? a series of large liquid bait stations strategically placed in the garden. Argentine ants love the pool of sweet poisoned liquid; other ants don’t.

One morning about a month after I put the baits out, I spotted an ant atop my computer screen.

To my amazement, it was single, large and red. A native harvester ant! It had apparently survived the gauntlet of Argentine ants. So maybe there is hope. Our native ants are still out there.

With a little help, and some selective Argentine ant control, maybe they can stick around. For my part, I plan to keep on with the bait stations.