Field abundance and nest structure of the ant Anoplolepis tenella associated with the African root and tuber scale in the Congo Basin

Anoplolepis tenella is a ground-dwelling ant of the tropical forest zone of Central Africa. It is associated with the African root and tuber scale (ARTS), Stictococcus vayssierei Richard, an emerging cassava pest in the zone. Developing sustainable and effective methods to control ARTS requires basic knowledge of the biology of A. tenella and the nature of interactions between the two insects. A study on the nest distribution and composition of A. tenella in various vegetation types prevailing in Central and South Provinces of Cameroon was conducted from April 2002 to June 2005. The results show that nests are generally built at the base of ARTS infested plants (96.2%; N = 469) - mainly under cassava plants (93.8%; N = 469).  Densities of A. tenella nests are higher in cassava fields (1600 nests per ha) compared with their densities in fallows (400 nests per ha), in secondary forest (90 nests per ha), and in primary forest (50 nests per ha). As with nest of other subterranean ants, the internal structure of A. tenella nest consists of cavities inter connected by a set of galleries. Relatively low percentage (13.7%, N = 51) of nests were queen-less, while those with queens were strongly polygynous (up to seven queens per nest) and with an estimate of 476 ± 255 (Mean ± SD) workers per nest. The brood (larvae and pupae) of sexual individuals appears in the nests from June to August, while sexual individuals can be found in the nests from June to September. Nuptial flights occurred between August and September. The high densities of the nests in disturbed areas in addition to polygyny are indications that A. tenella may share some characteristics with tramp ant species.