Policing against selfishness is now regarded as the main force maintaining cooperation, by reducing costly conflict in complex social systems. Although policing has been studied extensively in social insect colonies, coevolution between policing and selfishness has not been fully captured by previous theories. Queen caste fate of female larvae in social insects is considered as a trait subject to policing, in which rearing workers coerce the larvae to limit development into queens (caste fate policing). Because there is increasing evidence that both larvae and workers are involved in queen-worker determination, the conflict over queen caste fate should be understood as coevolution between policing workers and selfish larvae. In this study, I developed a two-trait quantitative genetic model of caste fate conflict in eusocial Hymenoptera. This model, originally developed for runaway sexual selection, allows for the analysis of coevolution between traits expressed in larvae and workers that collectively determine the larval caste fate. When the coevolution takes the form of arms race, caste fate policing coevolves with exaggerated selfishness of the larvae achieving maximum potential to develop into queens. The present model highlights the importance of understanding social traits as influenced by the coevolution of conflicting genomes.