To investigate the function of maternal care and determinants of reproductive Success in the subsocial bug Elasmucha putoni (Heteroptera: Acanthosomatidae), I used two different approaches, the measurement of phenotypic selection and female-removal experiments under conditions differing in biotic-em iron mental pressure. For two field populations, unattended eggs and younger nymphs consistently suffered severe predation pressure and attendance by parent females greatly enhanced their survival. In contrast, under enemy-excluded conditions, offspring performance was riot reduced in broods without parent female indicating that maternal care functions as a physical defense against predators. However, the determinant of female reproductive success in E. putoni in the field was not the care behavior alone. Selection gradient analysis showed that early season oviposition and larger clutch size, as well as a longer duration of care by it female, was favored during the breeding episode. This study is the first to evaluate phenotypic selection on parental care and other reproductive traits in arthropods.