Blackfly Aphis fabae overwinters as eggs on shrubs such as common spindle (Euonymus europaeus), Viburnum and Philadelphus. Egg hatch occurs in spring as the winter host plant is coming into new leaf. Several generations of wingless aphids, which are all female and produce live young rather than eggs, develop on the spring foliage. By May, the foliage on the winter host plants has become older and tougher, which along with increasing day length induces a change in the aphids. A generation of female winged aphids develops that fly away in search of suitable summer host plants, such as beans, nasturtium, poppies and dahlia. At that time of year male aphids are not required for reproduction, so a single winged aphid arriving on a broad bean can quickly establish a new colony. Blackfly infestations on the winter-spring host plants die out during May-June.
At the end of summer, another winged generation of aphids is produced that migrates back to the winter host plants. At that time there are males and females that will mate before the females deposit eggs around buds and in crevices on the stems.