During the growing season pea aphids reproduce by parthenogenesis: unfertilised eggs develop into female clones, and the embryos are retained and born live rather than laid. Because embryonic development begins before the mother herself is born, a newly deposited nymph can already contain her own daughters. Entomologists call the arrangement telescoping generations, and it compresses the interval between generations well below the time an individual takes to mature.
The result is exponential growth on a good host plant, checked mainly by predators, parasitoid wasps and the plant running out of usable sap. In autumn, shortening days trigger the production of males and egg-laying females, and the winter is passed as a fertilised egg.
The pea aphid holds a further oddity. It carries genes for making carotenoid pigments, acquired at some point by horizontal transfer from fungi, making it one of the few animals known to synthesise its own carotenoids rather than obtaining them from food.