The morphological ontogeny of Ceratozetes helenaePavlichenko, 1993 and Ceratozetoides cisalpinus (Berlese, 1908) is compared. The adults of both species have 10 pairs of short or minute notogastral setae, including c₂, but the former species is smaller than the latter and also differs by the location of some notogastral setae, shape of porose areas and setae on the legs and absence of seta l” on tarsus II; in Cer. cisalpinus this seta is present. The juveniles of these species differ from one another more than the adults. In C. helenae most gastronotal setae are short and plumose, whereas in Cer. cisalpinus they are long, curved anteriorly and barbed. In the former species most of the gastronotal setae are inserted on sclerites, and glabrous sclerites are also present on the gastronotum, whereas in the latter species these setae are inserted on unsclerotized integument, except for some dorsal setae of the nymphs which are inserted on weakly formed microsclerites, and a few glabrous microsclerites are present. Moreover, the subsequent nymphs of C. helenae are smaller than those of Cer. cisalpinus, especially the tritonymph. The morphological ontogeny of C. helenae and Cer. cisalpinus is compared with that of other species of Ceratozetinae (Ceratozetidae), and based mainly on the morphology of the juveniles, a new cryptic species, Ceratozetes shaldybinae sp. nov. is proposed.