The following information accompanied stocks donated to the Bloomington Stock Center by Martin Kracklauer, University of Michigan. The mutations and constructs described here relate to CG6589, which is currently named giacomo (giac) in FlyBase. Kracklauer prefers the symbols Dspag4 or spag4 based on its likely orthology to mammalian Spag4 (sperm-associated antigen 4). spag41 and spag46 are ends-out homologous recombination knockouts marked with a white allele. Both alleles are homozygous male sterile and female fertile. P{spag4.GFP} is a pP{CaSpeR-4}construct in which genomic spag4 is tagged with GFP, resulting in GFP fused to the spag4 protein C terminus. A synonym is Dspag4:GFP . P{spag4.GFP}1 is a homozygous and hemizygous viable and fertile, X chromosome insertion. P{spag4.GFP}3 is a homozygous viable and fertile, third chromosome insertion. P{spag4.6xMyc} is a pP{CaSpeR-4}construct in which genomic spag4 is tagged with six Myc tag sequences, resulting in six copies of the Myc tag fused to the spag4 C terminus. A synonym is Dspag4:6xMYC . P{spag4.6xMyc}2 is a second chromosome insertion. P{spag4.6xMyc}3 is a third chromosome insertion. Both P{spag4.GFP}and P{spag4.6xMyc} rescue the male sterility of spag4 null homozygous males. P{GFP.spag4} is a pP{CaSpeR-4}construct in which genomic spag4 is tagged with GFP, resulting in GFP fused to the spag4 N-terminus. A synonym is GFP:Dspag4 . This transgene does not rescue the sterility of spag4 null homozygotes, but the protein localizes to spermatid basal bodies. Specifically, it localizes to the entire basal body of spermatids only when the basal body is coming unmoored from the spermatid nucleus, the distal basal body when it remains anchored in the spermatid nucleus, and basal bodies only in postmeiotic spermatids. P{GFP.spag4}3 is a third chromosome insertion.