Life cycles

Life cycles and reproduction

The aphids use two methods of reproduction, sexual and asexual or parthenogenesis. The sexual females are oviparous whereas the parthenogenetic females are viviparous. They give birth directly to young larvae genetically identical to them, able both to feed themselves and move around immediately on emerging. The offspring of a parthenogenetic female are therefore clones. Aphids are multivoltine and can have up to 20 generations per year, depending on climate conditions. Their life cycles are highly variable

A complete cycle, or holocycle, entails one sexual generation and several asexual generations per year. In this case, the fertilized egg is laid in the summer, in a state of diapause which for the species is a strategy for survival during unfavourable weather conditions in winter. Hatching of the egg (see the video) generally occurs at the same time as buds are starting to open. The parthenogenetic female so produced is called the fundatrix or stem mother. She is nearly always apterous.
During spring, the fundatrix engenders one or several generations of parthenogenetic females, called fundatrigenia, which develop on the same plant as she does. The first generations are essentially made up of apterous forms, but then the proportion of alates gradually increases with time. The alate fundatrigenia leave their winter plant in order to colonize new ones.
Some species of aphid, known as monoecious ones, accomplish their whole development cycle on just one type of plant. The host plants colonized in spring are therefore the same or very closely related species as the winter ones.
Other, dioecious or heteroecious species (about 10% of species) alternate between two types of plants that botanically are very different. The plant serving as the site for sexual reproduction is termed the primary host and those the aphids migrate to during summer the secondary hosts. In spring, migration is achieved by the alate fundatrigenia (emigrants) which once on the secondary hosts give birth to a new generations of apterous  and alate parthenogenetic forms (see the video) called virginogenia.
In the autumn  parthenogenetic females called sexupara appear which will give birth to males (sexupara andropara), oviparous females (sexupara gynopara) or both (sexupara amphotera). After copulation (see the video) the female lays eggs (see the video).
In dioecious species, return migration back to primary hosts is done by the alate sexupara (type 1 dioecious holocycle) or by gynopara and alate males (type 2 dioecious  holocycle). Males and oviparous females meet each other on the primary host. Once fertilized, those females lay their eggs on the ligneous parts of their host plants.
The loss of the sexual phase has appeared in almost all aphid subfamilies. Where this has happened, the species reproduces throughout the year but only by parthenogenesis. This is referred to as the anholocyclic strategy. It occurs both in monoecious and dioecious species. Mild winter conditions favour this process. The tropical aphids for example are almost all anholocyclic but also most of the aphid pests of temperate environments.
This variability in reproductive cycles can also exist within the same species where some populations are anholocyclic and others holocyclic, depending mainly on how harsh the winter is and the availability of primary hosts. This is the situation for example in crop-destroying aphids such as Myzus persicae or Rhopalosiphum padi. The two types of cycle can coexist in the same region.

Modification date: 14 June 2024 | Publication date: 02 March 2010 | By: Evelyne Turpeau, Maurice Hullé, Bernard Chaubet