PREFERENCES OF THE FIRE ANTS SOLENOPSIS-INVICTA AND S-GEMINATA (HYMENOPTERA, FORMICIDAE) FOR AMINO-ACID AND SUGAR COMPONENTS OF EXTRAFLORALNECTARS

Extrafloral nectar, a solution of both sugars and amino acids that is produced by plants on stems and leaves, attracts ants that often prote ct the plants from potential herbivores. To understand better the ecol ogical significance of variability among plants in nectar chemistry, t he effectiveness of ant attraction by different extrafloral nectars wa s compared for nectar mimics that varied in either amino acid or sugar content. Workers of the fire ants Solenopsis invicta Buren and S. gem inata (F.) were fed on artificial nectaries containing mimics of pre- and postdefoliation nectars of Impatiens sultani, which differed in am ino acid content. Workers of the two fire ant species also fed from ar tificial nectaries containing mimics of Passiflora ambigua, P. talaman censis, and P. quadrangularis, which varied in sugar composition. S. g eminata workers preferred the more amino acid-rich postdefoliation mim ic over the predefoliation mimic. S. invicta did not discriminate betw een the two nectars, demonstrating that richer amino acid solutions ar e not more attractive to all ants. In the sugar experiments, both spec ies of ants preferred the nectar of P. ambigua over those of the other two Passiflora species. The nectar of P. ambigua had the lowest total sugar concentration and the lowest calorie content, indicating that a nts do not necessarily maximize sugar energy intake as they forage. Th e behavior of S. geminata and S. invicta shows that both amino acid an d sugar content can affect ant recruitment to plants and that differen ces in levels of recruitment cannot be predicted accurately based on s imple assumptions of nutrient maximization or energy content.