They are ectoparasites of a wide range of host species, and some are vectors of pathogens that can cause human disease.

[citation needed] They are distinguished from the Argasidae by the presence of a scutum.

[2] In both the nymph and the adult, a prominent gnathosoma (or capitulum, mouth and feeding parts) projects forward from the animal's body; in the Argasidae, conversely, the gnathosoma is concealed beneath the body.

[citation needed] They differ, too, in their lifecycle; Ixodidae that attach to a host bite painlessly and are generally unnoticed, and they remain in place until they engorge and are ready to change their skin; this process may take days or weeks.

[3] The family contains these genera:[3] Many hard ticks are of considerable medical importance, acting as vectors of diseases caused by bacteria, protozoa, and viruses, such as Rickettsia and Borrelia.