Argasids are tough, leathery ticks in which there is little differention between the sexes. Three genera of argasids, Argas, Ornithodorus and Otobius, contain species of medical and/or veterinary importance. In Ornithodorus there is no lateral sutural line and no distinct margin to the body. Adults and nymphs have a leathery cuticle with innumerable minute elevations termed mammillae. The hosts are varied, including reptiles, birds and mammals and the genus is worldwide in distribution. Aside from a few species parasitic on bats or tortoises in humid areas, most Ornithodorus occur in xeric climates. Ornithodorus talaje has been collected from a wide variety of hosts and in Brazil it has been found in wild rodents and bats.
Ornithodorus ticks commonly infest animal burrows, and prefer to hide in narrow cracks or under sand. According to the species the larvae either feed rapidly or remain within the open egg shell without feeding until they moult to nymphs. The life cycle cab be as short as two months, but adults can live for several years without feeding.