On a collision course with ants

NATURAL PERSPECTIVES

Aw, crikey, we’ve got ants! Even Aussie crocodile hunter Steve

Irwin would be hard pressed to come out on top in a battle with these

imported 6-legged horrors.

Argentine ants arrived in Southern California in the 1890s, most

likely as stowaways in a shipload of coffee or sugar from South

America. These tiny black ants like cooler, moister conditions than

Southern California’s larger native ants. The invaders found these

conditions in irrigated urban landscaping. As human development

spread, so did Argentine ants. In many areas, they have pushed out

native ants.

In Argentina, genetically different colonies of Argentine ants

fight to the death, which keeps the population under control. But in

California, the population spread from only a few individuals. They

recognize each other as genetically similar and don’t fight among

themselves, only with other species. Argentine ants have formed what

is essentially one giant colony that stretches from San Diego to

north of San Francisco.

The invading ants affected the ecosystem. Who would have guessed?

A hundred years ago, coastal horned lizards thrived in the wilds of

Huntington Beach. These lizards, popularly called horny toads, fed on

a variety of large native ants, including the carpenter ants that

used to live here.

For unknown reasons, coastal horned lizards don’t like to eat the

Argentine ants that replaced the native ants. Maybe Argentine ants

are harder to catch. Maybe they don’t taste good. Or maybe they’re

toxic. Whatever the reason, when captive young horned lizards are fed

a diet of Argentine ants, they not only fail to grow, they actually

lose weight.

As the lizards’ preferred habitats of coastal sand dunes and thick

chaparral were gobbled up and fragmented by development and as native

ants were out-competed by Argentine ants, the horned lizard

population plummeted. They were common years ago, but you’d be hard

pressed to find a coastal horned lizard at Bolsa Chica these days.

They are now candidates for listing as an endangered species.

Argentine ants spelled bad news for native ants and horned

lizards. They’re not much fun for humans either. When it rains in the

winter, Argentine ants invade our homes. Kitchens and bathrooms all

over town are turned into horrific sci-fi movie scenes as thousands

of insects swarm over fixtures and floors.

Native ants are an important part of the ecosystem. They turn over

and aerate soil, act as scavengers by eating dead invertebrates, and

disperse and bury seeds. But Argentine ants aren’t like native ants.

They don’t bury seeds or serve as food for horny toads. Where

Argentine ants are allowed to spread, pests such as aphids,

mealybugs, scale insects and whiteflies can flourish because

Argentine ants kill their natural predators, ladybugs.

Before you reach for the Raid, here are environmentally friendly

ways to control pesky ants. One time-honored method is to pour very

hot or boiling water over an ant mound. That’s fine and dandy if

there are no plants growing nearby, but many of us have landscaping

covering every square inch of our tiny yards.

Spraying Windex or other window cleaner with ammonia on an ant

trail will kill the ants it contacts. The ammonia also neutralizes

the formic acid that the ants secrete to mark their trails. Without

their formic acid trail, the ants get lost and can’t find their way

back to their food source or their colony.

In the vegetable garden, diatomaceous earth may help control ants.

Diatomaceous earth is a fine powder composed of the brittle

exoskeletons of microscopic diatoms, which are part of ocean

plankton. It isn’t toxic, but it is abrasive. When ants or other

insects crawl over it, the diatomaceous earth rubs away their hard

outer covering, which desiccates them. The ants don’t like to cross a

barrier of this stuff as long as it’s dry, but they’ll march right

over it when it’s damp. They may even tunnel under it. Crikey. Grab

the insecticidal soap spray.

Bait stations are a fairly safe control method. Because the ants

must crawl into the bait station to get the poisoned food, it can be

used around pets and it won’t kill other insects. Raid makes an

effective ant bait containing N-ethyl-perfluorooctanesulf- onamide,

which probably works by twisting the tongues and frying the brains of

the ants when they try to read that chemical name. Just kidding. The

chemical is also known as Metastop and Sulfluoramid. It prevents the

ants from converting their food into energy. It will kill off the

workers and the queen within a couple of weeks.

Insect growth inhibitors such as fenoxycarb, methoprene, and

pyriproxyfen kill developing ant larvae, but worker ants will

continue working until they die a natural death. This can take

several months. Growth inhibitors will kill other insects too, so we

don’t recommend scattering them over the landscape. We don’t like

insecticides such as diazanon or malathion either because people,

pets, wildlife and beneficial insects are exposed to it. When it

rains or the yard is over-watered, insecticides can be washed into

the wetlands and ocean.

Argentine ants are so entrenched by now that we’ll never eradicate

them. At our house, we co-exist with them, as long as they stay

outdoors and don’t become too numerous.

* VIC LEIPZIG PhD and LOU MURRAY PhD are Huntington Beach

residents and environmentalists. They can be reached at

[email protected].