Deaf1^S10B/Df(3L)25-21 zygotically mutant embryos develop normal first instar larval cuticles. Large numbers of either Deaf1^S10B/+ or Deaf1^S10B/Df(3L)25-21 embryos derived from homozygous Deaf1^S10B female germline clones (i.e. lacking maternal but not zygotic or lacking both maternal and zygotic Deaf1 function respectively) are laid, but approximately 70% of these embryos show developmental arrest at early stages of embryogenesis, prior to the onset of gastrulation and germ band extension. The few embryos that complete embryogenesis have segmental pattern defects, ranging in severity from mild to very severe. The range of cuticular defects in embryos lacking both maternal and zygotic Deaf1 function is similar to the range of defects in embryos lacking maternal but not zygotic Deaf1 function. The defects consist of loss and fusions of segments, affecting all parts of the anterior/posterior axis of the embryo. In the least affected embryos, defects are more frequently seen in the A5-A7 abdominal segments.