Macrophotograph of the peach aphid Myzus persicae on the stem of a stinging nettle plant Urtica dioica. This is an example of parthenogentic birth, the development of the egg without fertilization. In early summer these large females (2-3mm long) are called stem mothers and produce a wingless generation of aphids like themselves. These young then produce a winged generation which are able to disperse to a secondary host plant.