Field and laboratory studies were conducted in 1998-2000 on the biology and life history traits of the overwintering cotton aphid morphs. Cotton aphids in California overwinter as both, viviparous individuals and eggs. Low numbers of aphid immature and adults were found on annual winter weeds such as whitestem filaree, prickly lettuce, shepherd’s purse, chickweed, and London rocket, and some individuals were also observed on the new growth of citrus trees throughout the winter. Conversely, large numbers of cotton aphid eggs were found on pomegranate orchards during the winter period. The pomegranate orchards surveyed during this study harbored substantial number of fundatrices (first generation of asexual aphids that develop from eggs) early in the spring (February), which in a few weeks built up to large aphid populations with numerous alates (April). These alates may play an important role in colonizing other spring-summer crops, making the pomegranate host a potentially important source of aphids in the San Joaquin Valley. The preliminary laboratory experiments showed that the sexual females (oviparae) required to mate to lay eggs, and that multiple mating in the females increased oviposition 2-3 times when compared to females that mated once. The average number of eggs produced by a multiple-mated ovipara was 4.5 eggs. Eggs required cold temperatures to break dormancy (< 6°C). The preliminary degree-day study showed that the aphid eggs can develop at temperatures above 5.55°C and require about 240 degree-days to hatch. In addition, the fundatrices can also develop at temperatures above 5.55°C and required 115 degree-days to reach the adult stage. The implications of these results in developing and designing alternative aphid management plans are discussed.