In this paper, we present field observations on paternal care in five species of harvestmen belonging to the family Gonyleptidae: Gonyleptes saprophilus, Neosadocus sp. (Gonyleptinae), Iguapeia melanocephala, Iporangaia pustulosa, and Progonyleptoidellus striatus (Progonyleptoidellinae). We also provide a critical reassessment of all cases of paternal care in harvestmen and examine the extent to which the available data can be used to test a recent theory on the evolution of exclusive male care via sexual selection. Eggs of the two Gonyleptinae species are laid inside natural cavities in trunks and in the soil, whereas eggs of the Progonyleptoidellinae are laid on the undersurface of leaves and are covered by a thick mucus coat. Females of the five species are iteroparous and the batches generally consist of eggs in several embryonic stages. This finding suggests that males have many mating opportunities and that they guard eggs laid by more than one female. Data from other four paternal harvestmen (Zygopachylus albomarginis, Lepchana spinipalpis, Ampheres leucopheus, and Cadeadoius niger) are quite similar and support most of the predictions of the theory on the evolution of exclusive male care via sexual selection. However, information supporting the prediction that males should be willing to guard unrelated eggs is ambiguous since in at least two species, L pustulosa and Z. albomarginis, vagrant males do not hesitate to eat the eggs of unprotected batches. There are several differences in the behavioral patterns of guarding male and female harvestmen. The evolution of maternal care was clearly driven by natural selection, whereas paternal care seems to be a sexually selected trait. Paternal care has apparently evolved independently several times in the order Opiliones and at least twice within the Gonyleptidae: once in the subfamily Gonyleptinae and once in the ancestor of the clade Caelopyginae + Progonyleptoidellinae.443577598