Walchiidae stat. n. differs from both Trombiculidae Ewing and Leeuwenhoekiidae Womersley by larval scutum lacking anteromedian setae and anteromedian projection with expanded sensillae, leg segments 7.6.6 without tibial solenidion and mastisetae on leg III (Φ³ or ti³ =0, fmt=0000), and lacking stigma and tracheae. Walchiidae stat. n. comprises two subfamilies including four tribes, and 17 genera and 17 subgenera, among them three new genera and eight new subgenera are proposed in the present article. Currently, this family has approximately 240 nominated species. If we consider the loss of the anteromedian setae as an apomorphy, then Walchiidae stands at the most advanced stage of evolution of sand-mite parasitism. Prolongation of the scutum in Walchiidae provided the great possibility of diversifying scutal sizes and shapes for this family compared to those of Trombiculidae and Leeuwenhoekiidae. It is rational to unify three sand-mite families, Leeuwenhoekiidae, Trombiculidae and Walchiidae, their larvae parasitic on vertebrates into a single superfamily, Trombiculoidea nec Welbourn, 1991, separable from Trombidioidea s.l. of arthropod parasitic larvae and standing at most advanced level of evolution of Parasitengona. Walchiid sand-mites are essentially an Old World family and best developed in the Oriental Region with the centre of development in Southeast Asia.