sentence: This might also occur in B. dorsalis , given the appearance of the pre-zygotic maternal Bdsrya transcript at 0 – 1 h. For Lucilia , however , the use of the nullo promoter avoided pre-zygotic cell lethality [ 86 ] , and our results would suggest that the use of the Bdnullo promoter , which initiates expression zygotically at 2 – 4 h , would also be preferable for an embryo-specific lethality system in B. dorsalis .