Last week's announcement of a second infestation of little fire ants on Oʻahu is the latest episode in the spread of one of the world's worst invasive species.

The state Department of Agriculture says the latest sighting involves 18 properties around Ahuimanu Road and crews were dispatched to treat the area.

Workers also again treated the Kaneohe neighborhood where the fire ants were detected in December. Eleven properties covering around Alokahi Street are within the infestation zone.

This follows the finding of fire ants on a plant sold in February at the Punahou Carnival. A Kaimuki woman reported that she and her infant were stung by the ants discovered near a staghorn fern plant bought at the annual fair.

So what should homeowners to do if they suspect or want to check for fire ants? The state Department of Agriculture has these tips:

Leave a thin coating of peanut butter on a chopstick in several areas around your property for about one hour.

Any ants collected should be sealed in a plastic bag and frozen in the freezer for at least 24 hours.

Drop off or mail the plastic bags to any Agriculture Department office. More instructions are available on a department informational flyer and online video.

If you suspect an invasive species on your property, call the state's pest control hotline, 643-7378.

Little fire ants were discovered on the Big Island in 1999 and have since spread widely through that county and to other major islands.

The ant stings can cause pain and welts lasting for weeks and pets stung in their eyes can go blind. The ants have also caused agricultural crop damage and forced the closure of plant nurseries. The cost of even partial eradication have been estimated in the millions.