Parthenogenesis

Greenfly on a rosebush

Parthenogenesis is a term in biology. It means virgin birth. It is an asexual form of reproduction found in females where growth and development of embryos occurs without fertilization by a male. It occurs in both plants and animals, and is much less common than sexual reproduction.

Some plants and animals can reproduce either sexually or asexually. A good example are the aphids, (e.g. greenfly) which multiply parthenogenetically during the height of summer, but turns to sexual reproduction as the weather gets worse.

Aphid giving birth to a nymph

At different times of the year, they can be viviparous (live birth) or oviparous (eggs). During spring and summer, aphids usually produce live young (nymphs) parthenogenetically. These female aphids may or may not have wings. Males only appear in any number at the close of the season. Females then give birth sexually during autumn, laying eggs. Therefore aphids are said to undergo cyclical parthenogenesis.