Protomagalhaensia richardsoni n. sp. (Apicomplexa: Eugregarinida: Blabericolidae) is described from the giant lobster cockroach, Henschoutedenia flexivitta (Dictyoptera: Blattaria: Blaberidae: Oxyhaloinae: Nauphoetini). Oocysts within the genus are dolioform with polar plates. Those of Protomagalhaensia granulosae, Protomagalhaensia wolfi, and Protomagalhaensia blaberae possess distinct apical spines and a sagittal depression that are absent or reduced in P. richardsoni and Protomagalhaensia cerastes. Oocysts of P. richardsoni are significantly longer with larger sporozoite-bearing cavities than those of P. blaberae, P. cerastes, P. granulosae, and P. wolfi (external oocyst length 8.07 μm vs. 7.42 μm, 7.50 μm, 6.87 μm, 7.56 μm, respectively; internal oocyst length 6.94 μm vs. 6.44 μm, 6.77 μm, 6.09 μm, 6.72 μm, respectively). All 5 species are also distinguished by unique oocyst length/width ratios. No unique morphological structure distinguishes among the gametocysts of Protomagalhaensia species, but gametocysts of P. richardsoni are significantly shorter than those of P. blaberae, P. cerastes, P. granulosae, and P. wolfi (gametocyst length 184.3 μm vs. 325.15 μm, 253.27 μm, 273.63 μm, 218.3 μm, respectively). No structurally unique morphological gamont feature distinguishes among species of Protomagalhaensia. Rather, species distinctions are morphometric in nature. In general, gamonts of P. richardsoni are readily distinguished from those of P. cerastes and P. wolfi based on size alone: the latter species being roughly half the size of P. richardsoni. Gamonts of P. richardsoni are most similar to those of P. granulosae and P. blaberae but with relatively smaller primites and more slender satellites.