The treehoppers exhibit several forms of social behavior which can be categorized in terms of nymphal aggregating habits and the role of parent females in offspring maturation. These are: 1) nymphs occur solitarily without parental involvement; 2) nymphs occur gregariously and interact with attendant ants without parental care; 3) nymphs occur gregariously interacting with both parent females and attending ants; 4) nymphs occur gregariously with parental care until offspring mature. This paper describes these forms and suggests that predation is a major selective force guiding the development and maintenance of sociality and ant mutulism in these insects.