The life of social insects centers around sedentary colonies that can
include individuals belonging to different patrilines or matrilines, w
ith a turnover of reproductives. The colony is a scene for both cooper
ation and conflicts, and the conceptual framework for the evolution of
social life and colony organization is provided by the kin selection
theory. Variable molecular markers make it possible to dissect kinship
within colonies, identifying patrilines and matrilines and estimating
genetic relatednesses. Such markers have been used to test hypotheses
on social conflicts between queens and workers (split sex ratio hypot
hesis), among workers (worker policing hypothesis), and among reproduc
tive females (skew hypothesis). The data from several species of ants,
bees, and wasps indicate that workers can obtain information on the g
enetic heterogeneity of their colonies and use that information to man
ipulate reproductive decisions. The social structure of colonies and t
he mode of colony founding affect the population-wide dispersal of sex
uals. Populations with multi-queen colonial networks have limited disp
ersal; females stay in their natal colonies, and mating flights can be
restricted. As a result, coexisting queens tend to be related to each
other, maintaining the genetic integrity of colonies, and populations
become spatially differentiated to an extent that can lead even to so
cially driven speciation.