It’s both bees and ants. The reproductive strategy is called haplodiploidy. Males are born from unfertilized eggs (haploid) and females from fertilized eggs (diploid).

This means that all the female ‘sisters’ in a colony are 75% related to each other, and more related to their siblings than they would be to their own offspring (only 50%). The social organization is (ostensibly) predicated on maintaining highest possible genetic fitness by caring for siblings instead of passing genes on to offspring.