A set of third chromosome mutant stocks derived by insertional mutagenesis using the P-element construct P{lacW}; most lines have a lethal or semi-lethal phenotype. The P{lacW} construct carries a w+mC mini-white visible marker, Ecol\lacZ enhancer trap sequences, and bacterial sequences that allow plasmid rescue (FBrf0049800).
It is not known to which if any of the P{lacW}S125011a or P{lacW}ms(3)S125011bS125011b insertions the lethality of the "1250/11" chromosome (caused by l(3)S125011S125011) maps (no non-complementing deficiency).