A new mutant long palpi (Lp was discovered following treatment with ethylmethanesulfonate. The mutant is co-dominant to the wild type allele, sex limited and is controlled by a locus in linkage group III. Homozygous Lp females which exhibit the longest palpal type also have reduced viability, do not readily mate, or lay eggs. Heterozygous Lp females have palpi intermediate in length and show normal viability and fertility. Males heterozygous and homozygous for Lp have normal palpi and are fertile. In crosses with three other linked loci the gene sequence was Lp-Adh-bw-ae and the recombination frequencies were as follows: Lp-Adh=22.5%, Lp-bw=38.6% and Lp-ae=50.3%. Thus Lp represents the current known terminal marker on linkage group III, now over 50 map units in length.