Aphids have fascinating and complex life-cycles, comprising of several different forms and numerous generations each year (4). The eggs overwinter on certain host plants, which in the black bean aphid are the spindle tree (Eunomys europaeus), or on Viburnum or Philadelphius plants. The aphids that hatch from these eggs in spring are all special wingless females, known as 'stem mothers'. These stem mothers are able to reproduce asexually through a process known as 'parthenogenesis' that does not involve mating. Furthermore, they do not lay eggs but give birth to live offspring, which are also females and able to reproduce without mating. The next generation to be produced are typically winged forms, and these undertake migrations to new plants. These summer hosts include a range of species such as beans, docks and spinach. Further bursts of asexual reproduction and live births on these hosts allow large populations to build up quickly on these plants. Winged and wingless forms are produced throughout the summer, with the winged forms allowing dispersal to new plants. Towards autumn, migration back to the primary hosts occurs. Sexual females are produced on the winter hosts and males mate with the females. It is on these plants that the mated females lay eggs which will overwinter, allowing the whole cycle to start once more the following year (4).
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