The behavior benefits her sister queen in allowing her to produce more offspring, and results in a greater production of nephews and nieces than her own sons and daughter. In order for altrusitic behavior to evolve, the sacrifice of fitness by an individual must be compensated by an increase in fitness of the individual's relatives in relation to their degree of relationship. So a female may have more of her genes passes on by rearing her younger sisters than by rearing her own daughters. Some parasitic wasps and sawflies also some other insects have haplodipoloid genetics and yet never evolved social behavior. 3. reuse of single nest favored, usually very high mortality of nests, but long standing ones likely to persist especially as population inhabiting it gets larger.
Most primitive termites live directly in wood they feed on.
More advanced build a nest and forage out from that to collect grass, wood or other diffuse sources of cellulose. Some bring it back to nest and grow fungus on it and eat that.