Overview

The family Argasidae comprises 5 genera and approximately 170 species¹.
The 5 genera are: Argasinae (e.g. spp. Argas reflexus, Argas vespertilionis), Ornithodorinae (e.g. spp. Ornithodoros hermsi, Ornithodoros coriaceus, Ornithodoros moubata²), Otobinae (e.g. sp. Otobius megnini³), Antricolinae, Nothoaspinae.

They lack the scutum and have a leathery cuticle. But most species bear a centrally located dorsal plate which is covered by tiny mammillae, ridge structures that protrude above the cuticle surface. Subcircular depressions termed discs, representing sites of muscle attachment, occur in characteristic patterns over the dorsal and ventral surface.

In the larvae, an oval dorsal shield is usually present, but this structure should not be confused with the ixodid scutum, which always located on the anterior part of the body. In adults and nymphs, the capitulum is recessed ventrally, subterminal, hidden from a dorsal view.
Eyes, when present, occur on the lateral surface of the body. The ventral organ of unknown function appears as a broad transverse ridge posterior to the anus .
The spiracles occur on the supracoxal folds between the coxae of leg III and IV1.
The coxal pores, representing the openings of the coxal glands are located between the coxae of legs I and II.
Male and female dimorphism distinguish only by the appearance of the genital pore.

Their peritreme is tiny and round. Teeth are missed on the hypostome, the area porosa is missing as well.

During their blood meal argasid ticks can increase their body weight 3-5 times because their highly folded integument allows extensive stretching without additional growth.