Parthenogenesis in Hexapoda: Entognatha and non-holometabolous insects

In hexapods, unlike the majority of animals, development without fertilization is a common phenomenon. They evolved a striking diversity of unisexual reproductive types that include a variety of modes starting from spontaneous parthenogenesis in females to the production of impaternate males with different variants in between. Many reports about parthenogenetic species have accumulated over time. Here, we present a review of various parthenogenetic hexapod groups with a particular focus on their chromosome systems and ploidy level. We show that conclusions about the reproductive mode often lack solid evidence and sometimes inefficiently demonstrate how parthenogenesis is maintained in corresponding groups. In this review, basal hexapods (Protura, Collembola, Diplura), primarily wingless insect groups (Apterygota') and non-holometabolous insects are listed with references to a variety of their unisexual reproductive modes.