Allonemobius shalontaki (Braswell) (Orthoptera: Gryllidae: Nemobiinae), a newly recognized species, was described on the basis of novel electrophoretic alleles and a unique male calling song. However, little is known about the species and the factors that isolate it from co-occurring species of Allonemobius (Hebard). We use electrophoretic markers to document sympatry of A. shalontaki with its congener Allonemobius socius (Scudder) and to follow the life cycle of the two species at two sites. The results indicate that there are phenological differences between the species. To confirm the phenological differences quantified in the field, we study patterns of egg development and hatching in the laboratory. Together with laboratory hybridization studies, these result demonstrate that A. shalontaki and A. socius are strongly, but not completely, reproductively isolated.