Study links success of invasive Argentine ants to d...( The ability of Argentine ants to cha...)

The ability of Argentine ants to change from carnivorous insect eaters to plant sap-loving creatures has helped these invasive social insects rapidly spread throughout coastal California, according to a new study, displacing many native insects and creating ant infestations familiar to most coastal residents.

Biologists at the University of California, San Diego and the University of Illinois at Urbana discovered the opportunistic, changing dietary preferences of Californias Argentine antsthe first time researchers have documented what these invasive ants actually eatby studying a population of ants for eight years in the foothills southeast of San Diego. An advance copy of their paper is being published online this week in the journal Proceedings of the NationalAcademy of Sciences.

Despite the fact that these species are known to cause ecological problems in many countries, scientists really didnt know what they eat, said David Holway, an associate professor of biological sciences at UC San Diego who headed the study conducted in California and Argentina.

Holway, Edward LeBrun of UCSD, and Chadwick Tillberg and Andrew Suarez of Illinois discovered that when Argentine ants first move into an area they become fierce predators of native insects, feeding on the blood of native ants and other insects. But as the ants eliminate their competitorsand their main source of foodover time, they switch from a carnivorous, protein-rich diet to a largely carbohydrate, sugar-water diet as they begin feeding on the honeydew nectar from aphids and scales.

Insights into the ants food sources were obtained through the use of nitrogen isotopes, which provided information about the relative amounts of protein and carbohydrate in their diets.

Honeydew nectar is essentially digested plant sap excreted by aphids and scales, said Holway. If youve ever parked your car under a tree and found your windshield covered with sticky stuff, thats ho
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