The association with honeydew producing insects has been hypothesized as a cause of invasiveness of many exotic ants. Honeydew contains sugary substances and amino acids, which provide nutrients particularly to workers of exotic ants (rather than native ants). As a reward for this carbohydrate-rich food, the exotic ants strongly protect the honeydew-producing insects from their natural enemies. Many researchers have empirically shown the latter effect, i.e. the attendance of some invasive ants improves the population growth of honeydew-producers. However, little is known about the honeydew producer’s effects on invasive ants. To investigate the honeydew producer’s effects on the colony growth and/or maintenance of invasive ants, we performed a laboratory experiment in which we reared colonies of the yellow crazy ant, Anoplolepis gracilipes, with or without a colony of honeydew producing mealybug, Planococcus citri. We found: (1) Ant colonies are statistically significantly better maintained in the existence of honeydew producers. (2) The life span workers was statistically significantly extended by the existence of honeydew producers. Our result is rare direct evidence of mutualism between honeydew-producers and the invasive ants tending.