These ants belong to the genus Camponotus and are commonly called Carpenter Ants. Mealybugs are scale insects, they pierce leaves and feed on sap. Excess sap concentrates as honeydew, which attracts ants. In a display of Mutualism, the ants provide them protection from predators.
Mutualism is a co-operative interaction between two organisms of different species where they biologically interact and derive some positive benefit out of the interaction. However, this is not an obligatory relationship. Both species can function normally without this relationship.