Effect of photoperiod on population parameters of two color morphs of the pea aphid Acyrthosiphon pisum Parasitism and offspring fitness of Aphidius ervi Haliday in relation to its host Acyrthosphon pisum Harris at different stages Effects of continuous UV-B stress on biological characteristics of green pea aphid Effect of photoperiod on growth and development of two color morphs of pea aphid (Acyrthosiphon pisum) Effects of UV-B radiation on biological characteristics of differentcolor pea aphid morphs (Acyrthosiphon pisum) Genetic Diversities of Acyrthosiphon pisum(Harris)(Pink form) Populations from Different Geographic Regions in the Northwest of China Effect of UV-B for Different Radiation Durations on Biological Characteristics of Two Color Morphs of Pea Aphid Acyrthosiphon pisum (Harris) Offspring