Transport and dispersal of Stictococcus vayssierei (Homoptera, Stictococcidae) by Anoplolepis tenella (Hymenoptera, Formicidae)

Dispersal can be a crucial factor affecting fitness in insects. We conducted a series of experiments and observations with the aim of determining the dispersal mode of the African root and tuber scale Stictococcus vayssierei, a pest on cassava in the Congo Basin. We monitored the main options of dispersal that occurred in scale insects: wandering of first-instar nymphs (crawlers), active dispersal by ant workers, phoresis on colony-founding queen ants, and passive dispersal by wind. Results showed that A. tenella workers are actively involved in the transport and dissemination of scale crawlers. When ants were excluded, crawlers could move by themselves for a short distance to find the host plant. In the presence of ants, crawlers were transported by ant workers for longer distance across the bridge and established on scale-free plants. Scales transport increased with the duration of the experiment and ant density. Neither a case of phoresis nor dispersal by wind was recorded, suggesting that passive dispersal is rare. These results outline the active role of A. tenella workers in the dispersal of immature stages of S. vayssierei in Southern Cameroon and have implication in the management of the scale on cassava.