The paper presents data concerning the progress of embryogenesis of the parasitic mite S. vespertiliones. The adaptation to the specific conditions of parasitism resulted in considerable alterations in the entire process of the embryonic period of ontogenesis. First of all, this led to the loss of vitellus ovi by the eggs (alecithal eggs), simultaneous adenotrophic development of a large number of embryos (up to 10), considerable embryonization in the early stages of ontogenesis - up to the protonymph. This results in the absence of an embryonized haxapod larva, progressive growth of the size of embryos in the process of their development, changes occurring in the course of blastulation (steroblastula) and gastrulation, as well as some peculiarities of the formation of the generative elements and the digestive system. The following stages of embryogenic development were singled out: cleavage; formation of embryonic layers; protolarval morphogenesis; larval morphogenesis; and protonymphal morphogenesis. However, all these considerable changes, occurring in the course of embryonic ontogenesis, cannot be regarded as an indicator of basic differences between the mites Spinturnicidae and the rest of the cohort, because these changes testify only of the advanced specialization of representatives of this family.