Parthenogenesis

Parthenogenesis is the development of an unfertilized egg into a complete new individual, entirely without fertilization ever taking place; the phenomenon was first discovered by Charles Bonnet in 1745, and it comes in two main forms, natural parthenogenesis and artificial parthenogenesis.

Natural parthenogenesis occurs regularly and spontaneously as part of certain animals' normal life cycle, and is itself of three kinds depending on the sex of the offspring produced: arrhenotoky, in which parthenogenesis produces only male offspring, as in honey bees; thelytoky, in which it produces only female offspring, as in Solenobia; and amphitoky, in which the parthenogenetic egg can develop into an individual of either sex, as in Aphis. Natural parthenogenesis is further classed as complete, where it is the only mode of reproduction an animal ever uses (with no biparental sexual reproduction and no male individuals at all, so the species is represented purely by females), or incomplete, where both sexual reproduction and parthenogenesis occur side by side in the same species - the honey bee again being the standard example, where fertilized eggs (zygotes) develop into queens and workers while unfertilized eggs develop into drones (males). A further specialised form, paedogenetic parthenogenesis (or paedogenesis), occurs when a larval stage itself produces a new generation of larvae by parthenogenesis, without ever reaching the adult form first; this is seen in the sporocyst and redia larval stages of the liver fluke, and also in the larvae of some insects, such as the gall fly. …