The segmentation defects previously reported to be due to the Ten-m05309, Df(3L)Ten-m-AL1 and Df(3L)Ten-m-AL29 mutations are not due to the Ten-m05309 mutation, but instead are caused in each case by a mutation in the opa gene (represented in by the oparSS allele) present on the TM3-rSS balancer in each original stock.