Venom attracts decapitating flies
Chemistry may help scientists improve control of invasive fire ants
A fire ant’s weapon is also its weakness. The insect’s venom attracts parasitic flies, which bring about a slow ant death that ends in decapitation, scientists report in an upcoming Naturwissenschaften.
By identifying venom alkaloids that attract the flies, researchers may be able to better monitor populations of the pests and their enemies and to design improved fire ant control strategies.
Fire ants were imported from South America in the early 20th century and, with little competition and no natural enemies, quickly became a major pest in the southeastern United States. Knowing that phorid flies were ant decapitators, scientists began releasing the flies as a biocontrol agent in the 1990s in the United States. But scientists didn’t know which chemical cues guided flies to their victim ants, and the control efforts, while successful in some areas, have not yet fully quelled the fire ant problem.
Fire ants have more than 10 glands, and which ones held the attractant wasn’t clear, says entomologist Henry Fadamiro of Auburn University in Alabama, who led the new research. Fadamiro and colleagues hooked electrodes up to the antennae of flies to investigate which of several stimuli prompted nerves to fire. By exposing the antennae to extracts from different ant glands and body parts, the researchers determined that juice from the venom glands got antennae buzzing. Fire ant venom is about 90 percent alkaloids, nitrogen-containing compounds that are often toxic. Separating the venom into its chemical components allowed the team to pinpoint specific compounds that the flies favored. Further tests, in which flies chose their favored scent, confirmed the antennae tests.