A survey of ants (Hymenoptera : Formicidae) that forage in vineyards in the Western Cape Province, South Africa

This study was undertaken to establish which species of ants were associate d with the mealybug Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae ), and which species were dominant in the main vine-growing areas of the We stern Cape Province, South Africa. During 1998/99, 22 vineyards were survey ed in the Stellenbosch/Paarl, Little Karoo, Worcester, Swartland, Olifants River and Hex River Valley regions, using pitfall traps to sample epigaeic ants and tuna-bait traps to sample arboreal ants. Each vineyard was sampled intensively for two consecutive weeks shortly before harvest. Forty two sp ecies of ants were recorded during the survey. The most widely distributed ant species, which were potentially dominant and associated with mealybug o utbreaks in vineyards in the Western Cape Province, were Anoplolepis custod iens (F. Smith), A. steingroeveri (Forel) and Linepithema humile (Mayrn). C rematogaster peringueyi Emery, Crematogaster sp. 2 and C. melanogaster Emer y are three arboreal species potentially dominant in vines only. Dominance indices for Pheidole sp. 1 and Pheidole sp. 2 were low compared to the more aggressive Anoplolepis spp. and L. humile, indicating that the former two species were not of economic significance. Edge effects occurred in five of the surveyed vineyards for three ant species. These edge effects indicate specific preferences of the ants for certain abiotic and microclimatic fact ors in vineyards, but could also be the result of interspecific competition .