Posted on: Monday, May 2, 2005

By Jan TenBruggencate
Advertiser Science Writer

There are no native ants in Hawai'i, but the tiny insects exist on every one of the major Hawaiian Islands as well as all the larger Northwestern Hawaiian Islands.

Forty-four species of ants have become established in the Islands, and at least twice that number have been detected at one time or another but have not become established, according to the Hawai'i Ecosystems at Risk Web site, www.hear.org.

They are an incredible pest, said Sheldon Plentovich, a zoologist at the University of Hawai'i who studies life on the state's small offshore islands.

Some species of ants prey on other insects. Some attack and kill newly hatched ground-nesting seabirds. Plentovich said adult birds are sometimes found with ant-covered wounds on their feet. Some ant species may eat plant seeds and some compete for habitat with native species.

But one of the things that may not be fully understood are the ants' indirect impact on plants.

Plentovich said that while the glaber ant mainly feeds on honeydew from aphids and mealybugs, it also competes for nesting places with the native yellow-faced bee. These bees collect nectar and pollen like honeybees but are solitary animals and do not form hives.

Several other ant species, such as the big-headed ant and the Argentine ant, may feed directly on the bees.

"When the big-headed ants are around, there are no native species," Plentovich said.

That's significant because native yellow-faced bees are important pollinators for a number of native plants.

One of the plants they pollinate is the endangered native shrub 'ohai, Sesbania tomentosa, a member of the pea family.

The attractive flowers of the 'ohai, which can be salmon-colored, orange-red or yellow, can't be pollinated by honeybees, since they're too big to get to the flowers' reproductive parts. But the smaller yellow-faced bees can.

"Sesbania have a very specialized flower morphology. Honeybees are too big to get to the stamen," Plentovich said.

Yellow-faced bees are also natural pollinators of the Maui silversword. But on that island, the Argentine ant is preying on the bees and reducing their populations, and researchers are worried about the impact on silverswords. For more on that, see the Haleakala National Park Web site, www.nps.gov/hale/pages/tier_two/pollinators_silverswords.htm.

If you have an issue, question or concern about the environment, contact Jan TenBruggencate at jant@honoluluadvertiser.com, (808) 245-3074 or P.O. Box 524, Lihu'e, HI 96766.