Groups of two or more consexual conspecific adults of many kinds of nonsocial insects have been observed to form at feeding, mating, ovipositional, or sheltering sites. Conversely, adults of these same insects have been observed to avoid joining consexual conspecifics (or their progeny) and to place themselves (or their progeny) at some distance that results in spacing. Examples from various taxa illustrate that mechanisms underlying joining or avoidance behavior differ among species, as do types of benefits and costs to individuals who decide to join or avoid others. Moreover, within a given species, the decision to join or avoid others can be affected markedly by the physiological and informational state of the individual and by contextual response thresholds to resource availability. Decisions that benefit the individual may or may not affect the group in terms of total reproductive output.