The scorpion Diplocentrus zacatecanus Hoffmann (1931) was originally described as a subspecies of Diplocentrus keyserlingi Karsch 1880 on the basis of six syntypes and was later elevated to species level. We designate a male lectotype and redescribe the species, including illustrations of the hemispermatophore of a male collected near the type locality. In this genus, the hemispermatophore is poorly sclerotized and lacks elaborate capsular structures, which are taxonomically useful in other genera. We review the variability in the hemispermatophores of males from one population, including five comparisons of the right and left hemispermatophores of the same males. Our results showed asymmetry in the length of the right and left hemispermatophores of the same individual. We also observed the presence of “crenulations” or “spines” in two different hemispermatophores (not complementary ones). We conclude that caution should be used when describing the hemispermatophore of only one male and considering it as diagnostic for the species, because of the high levels of intraspecific variation.