One copy of bcd^K57R is not sufficient to rescue bcd⁶/bcd⁶ lethality (100%), with 69% of embryos exhibiting an unhatched phenotype. Of the hatched embryos, 50% exhibited larval head defects. Two copies of bcd^K57R partially rescues bcd⁶/bcd⁶ lethality, with 25% of embryos failing to hatch. Of these that do hatch, 36% exhibit larval head defects such as reductions in the dorsal arm, dorsal bridge, and labrum, or moderate to strong defects such as the absence of discernable head skeletal structures and general disorganisation of the head. Approximately 10% of embryos lack head and thoracic structures entirely and contain a posterior duplication. One copy of bcd^S35T, with one copy of bcd^K57R in a bcd⁶ homozygote background partially rescues the bcd⁶ embryonic lethality phenotype, with 31% of embryos remaining unhatched. Of those that do hatch, 26% exhibited larval head defects.