Consequences of foundress aggregation in the brown citrus aphid Toxoptera citricida

1. A field study was conducted in which colonies of Toxoptera citricida (Kirkaldy) were initiated with different numbers of foundresses on ungrafted citrus trees var. ‘Carrizo’ within an existing citrus grove in central Florida. 2. The growth rate, longevity, and final size of T. citricida colonies were all positively correlated with number of foundresses. 3. Colonies initiated by many foundresses produced alatae earlier than those initiated by fewer foundresses. 4. Nymphal developmental time was reduced in colonies initiated by more foundresses but the mean number of grand‐progeny per foundress was lower when only surviving colonies were compared. 5. The longevity of foundresses was unaffected by their number but foundress fecundity and nymphal survival decreased as foundress number increased. 6. The most abundant natural enemies were Diptera: Syrphidae, primarily Pseudodorus clavatus (F.), and Chamaemiidae (Leucopis sp.), followed by Coleoptera: Coccinellidae, primarily Cycloneda sanguinea (L). 7. Colonies initiated with more foundresses attracted more oviposition by dipteran predators than did colonies initiated with fewer foundresses.