The Argentine ant Linepithema humile(Mayr) was found to be disruptive to the black scale Saissetia oleae Olivier, parasitoid Coccophagus scutellaris (Dalman) in California (Horton, 1918). In South Africa Metaphycus helvolus (Compere), a parasitoid of black scale was found to be effective in the absence ofL. humile(Flanders, 1943; Compere, 1940). In California,Daane et al. (2007)found that L. humile promoted populations of obscure mealybug Pseudococcus viburni (Signoret) while lowering populations of its parasitoids Pseudaphycus flavidulusandLeptomastix epona. They also noted increased densities of the Argentine ant-tended grape mealybug Pseudococcus maritimus(Erhorn) accompanied by a serious reduction in its parasitoid populations.