Sharpshooter threatens Tahiti by inedibility.

In a new twist on invasive-species biology, a North American insect is menacing Tahitian ecosystems by getting itself killed and proving surprisingly toxic to its predators.

The invader is a half-inch-long leafhopper called the glassy-winged sharpshooter (Hornalodisca coagulata). It's native to the southeastern United States and northern Mexico, but it reached California in the 1980s. It's a strong flyer and has proved an unusually fast spreader of pathogens such as those for phony peach disease or for Pierce's disease, which can kill a grapevine in 2 years.

Now, the sharpshooter has reached French Polynesian islands including Tahiti and Mo'orea, where it's bringing trouble to paradise, warn two University of California (UC) researchers. Kenwyn Blake Suttle of UC-Berkeley and Mark Hoddle of UC-Riverside say that it's too early to tell whether sharpshooters will bring plant epidemics to the South Pacific.

Sharpshooters are already a local nuisance, though. Known as mouches pisseuses, they grow into denser populations in Tahiti than they do in California. Anyone standing under a tree where sharpshooters are drinking and excreting sap can get unpleasantly damp.

Native Polynesian spiders face a more serious threat from the sharpshooters, Suttle and Hoddle report in an upcoming Biological Invasions. No one has reported North American spiders troubled by sharpshooters. How ever, when the researchers fed the insects to two species of native Tahitian spiders, 47 percent of the spiders died within an hour, apparently of intoxication.

In fact, the researchers note that some crab spiders collected from island spots infested with sharpshooters walked away from the potentially enticing meal, suggesting that those spiders may have had a previous unpleasant encounter.--S.M.