No migration of border follicle cells is seen in mosaic egg chambers in which all border cells are mutant. If the only wild-type cells in the border cluster is one or both of the anterior polar cells (APCs), migration is not initiated. If one or two outer border cells are wild-type, these initiate movement but remain associated with the mutant border cells and the cluster moves very little. If one or two outer border cells are mutant, these mostly remain associated with the wild-type border cells and are "dragged along" at the rear of the cluster. If one or both APCs are mutant, this does not affect the migration or position of the cell. Border cells fail to migrate in slbo01310/slbory8ex2d egg chambers.