Sociality occurs in less than one percent of all arachnids. Prolonged subsocial behavior with amicable mother-offspring-sibling associations that extend for a year has recently been reported in captive amblypygids, Damon diadema Simon 1876 (whip spiders; order Amblypygi, family Phrynichidae; Rayor & Taylor 2006). Many social animals have the ability to discriminate kin from other conspecifics so that benefits of group-living are preferentially directed toward kin, although kin discrimination is rare in social spiders. To aid in quantifying rates of behavior, we developed a behavioral ethogram of social and agonistic interactions in immature D. diadema. We conducted two experiments that demonstrate the ability of immature D. diadema to recognize and behave differentially toward kin. In a series of cross-introduction experiments, immature kin or non-kin were introduced into social groups to determine whether aggression and non-aggressive interaction rates varied based on their relationship to the resident animals. To test the hypothesis that differences in behavior were due to familiarity with the habitat, rather than with kinship with resident animals, individuals were cross-introduced into unfamiliar habitats with kin or non-kin. In these introduction experiments, kinship determined the level of aggression among individuals while habitat familiarity did not have an effect. Using olfactory cues alone in Y-maze choice experiments, 9-month old amblypygids discriminated their mother from an unrelated adult female and spent significantly more time near their mother. We discuss our results in relation to other examples of kin discrimination in insects and arachnids, and potential benefits to amblypygids at different ages.