spo^Z339 embryos show normal development until stage 14. After this stage, spo^Z339 embryos exhibit head involution failure, an absence of midgut and dorsal closure, an abnormal hindgut looping and a lack of cuticle differentiation. These defects are seen at the same level in embryos from spo^Z339 germline clones and zygotic mutants, indicating that there is no spo^Z339 maternal contribution.

spo^Z339/spo^Z303 embryos rarely hatch. When an artificial pulse of 20E is delivered to these embryos midway through embryogenesis, approximately 30% survive to hatch and 20% survive to adulthood. Rescued spo^Z339/spo^Z303 females produce no progeny due to arrest of egg development at stage 8 of oogenesis, while rescued males are fertile.

An artificial pulse of E allows 25% of spo^Z339/spo^Z303 embryos to hatch and 12% to become adults. A pulse of ketotriol allows 13% to hatch but only 1% survive to become adults. In contrast, pulses of ketodiol and 7dC do not rescue the lethality of spo^Z339/spo^Z303 embryos at all.