Embryos laid by females expressing bves^a.hs (driven by heat shock) show a much lower survival rate than embryos laid by wild-type heat-shocked females. Posterior midgut invagination does not occur normally in almost 10% of embryos laid by females expressing bves^a.hs, with pole cells being left behind at the posterior end. In 20% of the mutant embryos, the gut opening fails to reach the head region at stage 8, resulting in a hole in the middle of the embryo.