Hermaphroditism is extremely rare in the insect world despite the comparatively common nature of this condition in the crustaceans. Several species of Icerya, including the pestiferous cottony-cushion scale, I. purchasi, are known to be hermaphrodites that reproduce by self-fertilising. Occasionally males are produced from unfertilised eggs, but generally individuals are monoecious with a female-like nature but possessing an ovotestis and sperm is transmitted ovarially from the female to her young. The existence of both hermaphrodites and males in a species is known as androdioecy. This hermaphroditic sexual self-sufficiency, where a single individual can populate new territory, has contributed to the invasive spread of the cottony-cushion scale insect away from its native Australia.