Two new species of Macrochelid acari Macrocheles novaodessensis, sp.n. and M. roquensis, sp.n. are described. These species inhabit cattle manure and were collected in several ranches in the state of São Paulo, Brazil.

Foram observados dois tipos de reprodução nos Ixodorrhynchi-dae: ovlparo, em Ophiogongylus Lizaso, 1983, e ovovivíparo, em Ixobioi-des Fonseca, 1934 e Chironobius Lizaso, 1983. São fornecidas descrições dos estágios imaturos e dados biológicos.

Two kinds of reproduction in the Ixodorrhynchidae were ob-served: oviparous, in Ophiogongylus Lizaso, 1983, and ovoviviparous, in Ixobioides Fonseca, 1934 and Chironobius Lizaso, 1983. Descriptions of the immature stages and biological data are given.

The ectoparasitic mite fauna of non-poisonous snakes from the Estado de São Paulo was surveyed during the period of March, 1976 to September, 1979. Considerations are made about the systematics and ecology of the genera studied. A total of 1969 snakes belonging to 30 genera was examined. This study also includes data on multiple parasitism, diversity of the mite fauna, abundance of each genera of mite, for the 4 families and 7 genera of mites.

Ectoparasitic mites on Brazilian non-poisonous snakes, collected from March 1976 to December 1979, are herein reported. A systematic study of the Ixodorhynchidae, which include exclusively parasites of snakes is given, including all immature forms. Two new genera are described: Ophiogongylus gen.n. with two species: Ophiogongylus rotundus sp.n. and Ophiogongylus breviscutum sp.n. and Chironobius gen.n. with two species: Chironobius alvus sp.n. and Chironobius nordestinus sp.n. Ixobioides brachispinosus sp.n. and the male of Ixobioides fonsecae (Fain) are also described. Immature forms, hosts relations and geographical distribution are given for the species.