Differential feeding responses in two species of nectivorous ants: Understanding bait palatability preferences of Argentine ants

Abstract

The Argentine ant, Linepithema humile (Mayr) (Formicidae: Dolichoderini), has become one of the most invasive species in the world, causing economic and ecological imbalances due to its ability to dominate new environments. Although borated liquid baits are effective for its chemical control, as well as for other nectivorous ants, there are particularities in the response of each species. In feeding-motivation controlled experiments, L. humile accepts boric acid more than borax (sodium borate); meanwhile, the opposite occurs with the carpenter ant, Camponotus mus (Roger) (Formicidae: Camponotini). To understand which aspects of the borax bait negatively affect its palatability for the Argentine ants, we analysed the individual feeding behaviour on sugar baits considering the number of boron-equivalents offered, the sodium concentration and the alkaline pH and then compared their response to that of C. mus. We found that L. humile rejected borax baits more than the mixture of boric acid and sodium borate. However, they accepted the boric acid bait similar to the plain sugar solution (control). The addition of sodium (NaCl) to sugar solutions shortened feeding time in this species, but not in the carpenter ant. Finally, alkalinizing the bait with L-arginine or potassium hydroxide (KOH) generated shorter intake times in L. humile, but not in C. mus. Our results showed that both the presence of sodium and a basic pH may discourage ingestion in the Argentine ant and also evidence the different responses towards the baits that can occur among ant species that share similar feeding habits. Understanding particular responses of the target Argentine ant is a key tool for more specific and efficient pest control strategies.