Comparative Studies on Aggregations among Aphids in Relation to Population Dynamics : II. Effects of Aggregation on the Growth and Fecundity of Brevicoryne brassicae L. and Myzus persicae : SULZER : Homoptera : Aphididae

The effects of aggregation on the growth and fecundity of the aphids, Brevicoryne brassicae and Myzus persicae, which coexist on cruciferous plants were compared. The body size of B.brassicae increased with the increase of aphids per leaf cage, while that of M.persicae did not. When newborn nymphs of M.Persicae were confined in a small leaf cage to form compact aggregations not usually seen in this species in nature and reared to the adult stage, the body weights and fecundity decreased. This harmful effect of overcrowding was seen on mature leaves more notably than on young leaves. Compact aggregatins of B. brassicae enhanced the growth of both conspecifics and M.Persicae possibly through improvement of nutritional conditions of leaf. The adaptive significance of two aggregation types (the compact aggregation and the loose aggregation) were discussed.