The role of aggregation in mediating the ecological parameters that influence survival and development in first-instar southern green stink bug,Nezara viridula(L.), was examined. Aggregated nymphs were able to survive and develop more rapidly than isolated nymphs at low relative humidities. Aggregation appeared to facilitate intake of atmospheric water and protect against desiccation. An acceleration of development in aggregated nymphs was observed at low temperatures. It was confirmed that first instars do not feed, so aggregation had no role in nutrient intake. Aggregation apparently does not function as a means of contacting essential symbiotes. Adherence to a substrate was facilitated by aggregations of up to 10 nymphs, at which point aggregation became multilayered. Aggregated nymphs suffered less predation byPodisus maculiventris(Say) andSolenopsis invictaBuren. Individuals as well as groups of nymphs were unpalatable toHippodamia convergensGuérin-Méneville.Monomorium minimum(Buckley) apparently learned nonpreference of first instars whileTertamorium guineense(F.) andPheidole dentatumMayr were undeterred from foraging for nymphs over time.