Parental care is any parental trait that enhances the fitness of a parent’s offspring, and that is likely to have originated and/or be currently maintained for this function. How parental care evolves and which sex should care for the offspring are central questions in evolutionary biology. The theoretical bases to address these questions were proposed almost 45 years ago, but recent models have challenged classical foundations and proposed new hypotheses. An in-depth account of these models is beyond the scope of this chapter. Updated numbers for the taxonomic distribution and frequency of the different forms of post-ovipositional parental care in insects are provided. These numbers are used to construct hypotheses on the transitions between systems of care, the selective pressures that favoured the origin of care, and the evolution of male care and biparental care. Finally, gaps in our knowledge and indicate possible directions for future studies are empahsized.