UC San Diego

As a result of accidental introduction, the invasive Argentine ant, Linepithema humile, has successfully invaded many parts of the world including the California coast. Argentine ants are extraordinarily effective in displacing native ants. This study aims to link animal behavior and growth to resource consumption. We examined how different diets affect Argentine ant behavior. We hypothesized that having a diet composed of both carbohydrate and protein may increase colony size and activity level rather than having a diet composed of only nitrogen-based protein. To test this hypothesis, we first conducted a greenhouse experiment in which we used the presence or absence of honeydew-producing black bean aphids, Aphis fabae, to manipulate carbohydrate resources given to the ants. Our results show that carbohydrate- based honeydew gave ant colonies a higher number of surviving workers and a lower trophic level. We then conducted a lab experiment in which we tested activity and growth potential of Argentine ants from different supercolonies and manipulated their access of carbohydrate. The results showed that having sugar in the diet increased colony activity, individual level aggression, and likelihood for worker survival, and greater colony growth. These results aid our understanding to the nutritional ecology of Argentine ants, and possibly related species of Hymenoptera.