This paper compiles several observations made on the biology of some species of Oribatid Mites. These observations are, mainly, about the description and the deposition behaviour of spermatophores and some trophic aspects of Damaeius verticillipes Nicolet, Hermannia gibba (C. L. Koch) and Steganacarits magnits (Nicolet); about the oviposition behaviour of Phthiracarius nitens (Nicolet); about the moult behaviour, the prelarva, the ’scalps’, the developmental period from egg to adult and the adult longivity of D. verticillipes; and about some aspects of the predation of H. gibba, and Achipteria coleoptrata (Linne) and Phthiracarius cf. testudineius (C. L. Koch) by respectively, Labidostomma luteum Kramer (Acarina Prostigmata) and Acrotrichis sp. (Coleoptera Ptiliidae).