Embryos derived from females carrying Hr783 homozygous germline clones (which lack maternal but not zygotic Hr78 function) have an increase in the instance of unhatched eggs and a decrease in the amount of fertilized embryos compared to controls. Hr783/Df(3L)79-2 mutants lacking zygotic Hr78 function die during the second and third larval instar, while Hr783/+ mutants without maternal Hr78 function display very low levels of lethality. During the molt between first and second instar larvae, the tracheae of Hr783/Df(3L)79-2 mutants begin to fill with gas, as occurs in wild type, but stop before this process is complete. This results in second instar larvae that have tracheal branches filled with fluid, either partially or almost completely. Such fluid filling is also seen in 7-9% of first instar larvae.
Mutants die as third instar larvae. Mutant larvae exhibit asynchronous development at the second to third instar moult, reduced size during the third instar, tracheal defect and failure to pupariate.