Bionomics of Pea Aphid, Acyrthosiphon pisum (Harris) on highland legume crops grown in Northwestern Ethiopia - The study was investigated pea aphid preference and performance determination, identification of susceptible growth stages of various legume crop varieties, flight patterns and field monitoring and seasonal dynamics. The study result revealed that all crop species and varieties were colonized by pea aphid. However, variations were observed in the growth rate of the aphids, their colonization, preferences and performance. Durations of pea aphids required to infest test faba bean varieties after exposure ranged 4 6 days in multiple choice & 5 - 11 days in dual choice tests. However, others infest within a day. Pea aphid preference and performance in dual choice tests varied depending on the combination of alternative choices. Pea aphid infestation in late crop growth stage (50 PS) showed high number of apterous and alate than early crop growth stages (6-LS) infestation. Number of total & filled pods and biomass weight of grass pea & lentil varieties infested at 50 PS were significantly higher than earlier stages infestation (50 FS and 6 - LS).