ASSESSING BENEFITS TO BOTH PARTICIPANTS IN A LYCAENID-ANT ASSOCIATION

We examined interactions between the ant Iridomyrmex nitidiceps and th e lycaenid butterfly Paralucia aurifera in southeastern Australia, and present data supporting the hypothesis that both participants benefit from their association. In the field, lycaenids persisted only on tho se host plants that ants subsequently colonized. In the laboratory, ly caenid larvae reared with ants were 31-76% heavier, developed 37% fast er, and commonly completed one or two fewer instars than larvae reared without ants. Ant tending also resulted in 20% heavier pupae, 69% sho rter pupal duration, and 5% larger adults as measured by forewing leng th; adults were not significantly different as measured by body length . We hypothesize that these positive effects occurred largely because ant-tended lycaenid larvae spent more time feeding than did untended l arvae. Field data documented that ants colonized host plants only afte r lycaenid larvae were present, indicating that ants actively maintain ed the association. In laboratory experiments, 40% more ant workers su rvived when lycaenid larvae were present than when they were absent, a lthough ant mass was not significantly affected. We hypothesize that t he survivorship effects occurred because ants consumed the lycaenid's nectary gland secretions, which contained considerable amounts of gluc ose and amino acids. Our results show that lycaenids can benefit from ants in ways other than, or in addition to, protection from natural en emies and that they incur minimal developmental costs from associating with ants.