P elements from two P-tagged alleles, stm A(P1) and stm A(P4), of the tempe
rature-sensitive paralytic mutant stambh A (stm A) were remobilized to deri
ve wild-type revertants and P excision lethals. stm Apt remutated to lethal
ity, while stm A(P4) reverted to the wild type. The P excision lethals are
not amorphic mutations, since they were weaker in paralytic phenotype (i) t
han the parental P-tagged allele and (ii) for deficiencies for stm A. The l
ethals collectively affected all stages of the life cycle, demonstrating th
at stm A(+) is needed throughout fly development.