The ant mosaic in Ghana cocoa farms: further structural considerations.
Abstract
The distribution of ants in a Ghana cacao plantation [cf. preceding abstract] was investigated in order to gain information for an integrated control scheme for cacao pests and diseases involving the manipulation of ant distribution. Eleven of 52 ant species sampled by the pyrethrum knockdown method were numerous and are termed dominant ants. Numerical abundance is also reflected in terms of biomass since on average Oecophylla longinoda (Latr.), Crematogaster striatula Emery and Macromischoides aculeatus (Mayr), the most numerous species, accounted for 70.6, 13.9 and 4.6%, respectively, of the total wet weight of the samples in which they occurred.The ant distribution found on cacao and shade trees supported the earlier suggestion that the dominant ants are distributed in a three-dimensional mosaic [cf. RAE/A 61, 397]. Both intra- and interspecific mosaics occur over limited areas. Unforaged zones or lacunae occurred in the mosaic. These were temporary occurrences and may have resulted from recently changed foraging routes, aggression between colonies or the response of ants to recent vegetational or food supply changes. Radioisotope labelling of colonies confirmed the block-like nature of the colony distribution of ants of the group of C. africana Mayr. The large areas dominated by intercommunicating nests of C. striatula having their own queens are not a reflection of the intraspecific mosaic. The entire area inhabited by C. striatula, however, constitutes a component of the interspecific ant mosaic. It is suggested that C. striatula may rely on large long-lived colonies for survival.