A colony of so-called bigheaded ants has been discovered in a Costa Mesa neighborhood and entomologists are attempting to determine how widespread the invasion is and how the reddish-brown insects arrived in California.
The ants, scientific name Pheidole megacephala, are native to Africa but are sometimes found in humid regions such as Florida and Hawaii.
Officials said the discovery of the colony in the Mesa Verde neighborhood appears to mark the first time these species of bigheaded ants have surfaced in California.
The ants pose no significant threat to humans — they don't sting or cause painful bites — but can displace native ant populations and pose problems for other insects as well as agriculture, said Richard Tiffer, a plant pathologist with the Orange County agricultural commissioner's office.
The bulbous-headed ants likely arrived in the state on a plant or in a shipment that was overlooked by agriculture inspectors, officials said.
UC Riverside entomologist Les Greenberg, who visited Costa Mesa on Monday to inspect the colony, concurred.
"It could've come in from a plant from another state, a fruit or something like that," he said. "There are lots of ways stuff gets moved around."
Tiffer said the future of Costa Mesa's exotic ants will be up to the California Department of Food and Agriculture, which could exterminate or leave them be.
In the meantime, officials have distributed fliers in Mesa Verde identifying the insects as "one of the worst invasive ant species."
Residents who have questions or believe they have spotted bigheaded ants are asked to call the Department of Food and Agriculture's exotic pest hotline at (800) 491-1899. They can also call Tiffer or Mike Bennett at the agricultural commissioner's office at (714) 955-0100.