Ixodidae


The Ixodidae are the family of hard ticks or scale ticks, one of the three families of ticks, consisting of 750 species, as of 2025. They are known as 'hard ticks' because they have a scutum or hard shield, which the other major family of ticks, the 'soft ticks', lack. They are ectoparasites of a wide range of host species, and some are vectors of pathogens that can cause human disease.

Description

The Ixodidae are distinguished from the Argasidae by the presence of a scutum. In both the nymph and the adult, a prominent gnathosoma projects forward from the animal's body; in the Argasidae, conversely, the gnathosoma is concealed beneath the body.
Ixodidae attach to a host bite painlessly and are generally unnoticed, and they remain in place until they engorge and are ready to moult; this process may take days or weeks. Some species drop off the host to moult in a safe place, whereas others remain on the same host and only drop off once they are ready to lay their eggs.

Classification

The Ixodidae is divided into two groups: the Prostriata and the Metastriata, distinguished by the position of the anal groove, which is anterior in the former, and posterior in the latter. The Metastriata are further divided into two lineages, Amblyocephalus and Haematobothrion. As of 2025, the Ixodidae is composed of 769 extant species in 18 genera, in addition to two fossil genera.
Fossil genera
  • †Compluriscutula - 1 species, Poinar and Buckley 2008 Burmese amber, Myanmar, Cenomanian
  • †Cornupalpatum - 1 species, Poinar and Brown 2003 Burmese amber, Myanmar, Cenomanian
The Ixodidae is also sometimes classified by its subfamilies, but the current formulations do not encompass all species. There are currently five recognised subfamilies:
  • Amblyomminae - comprising Amblyomma.
  • Bothriocrotoninae - comprising Bothriocroton.
  • Haemaphysalinae - comprising Haemaphysalis.
  • Ixodinae - comprising Ixodes.
  • Rhipicephalinae - comprising Dermacentor, Margaropus, Rhipicephalus, ''Rhipicentor, Hyalomma and Nosomma''.

    Medical importance

Many hard ticks are of considerable medical importance, acting as vectors of diseases caused by bacteria, protozoa, and viruses, such as Rickettsia and Borrelia. Other tick-borne diseases include Lyme disease, babesiosis, ehrlichiosis, Rocky Mountain spotted fever, anaplasmosis, Southern tick-associated rash illness, tick-borne relapsing fever, tularemia, Colorado tick fever, Powassan encephalitis, and Q fever. Ixodid ticks are the primary vectors of tick paralysis, which can affect domestic dogs, cats and livestock, as well as humans.