The Ixodidae are the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

of hard ticks or scale ticks, one of the three families of

tick Ticks (order Ixodida) are parasitic arachnids that are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, species, and "fullness". Ticks are external parasites, living by ...

s, consisting of over 700 species. They are known as 'hard ticks' because they have a

scutum The ''scutum'' (; plural ''scuta'') was a type of shield used among Italic peoples in antiquity, most notably by the army of ancient Rome starting about the fourth century BC. The Romans adopted it when they switched from the military formati ...

or hard shield, which the other major family of ticks, the 'soft ticks' ( Argasidae), lack. They are ectoparasites of a wide range of host species, and some are vectors of pathogens that can cause human

disease A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...

Description

They are distinguished from the Argasidae by the presence of a scutum. In both the

nymph A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label=Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are ty ...

and the adult, a prominent

gnathosoma The gnathosoma (from Greek , ' = "jaw" and , ' = "body") is the part of the body of the Acari (mites and ticks) comprising the mouth and feeding parts. These are the hypostome, the chelicerae and the pedipalps. It is also called the capitulum (howe ...

(or capitulum,

mouth In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on ...

and feeding parts) projects forward from the animal's body; in the Argasidae, conversely, the gnathosoma is concealed beneath the body. They differ, too, in their

lifecycle Life cycle, life-cycle, or lifecycle may refer to: Science and academia * Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring *Life-cycle hypothesis ...

; 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. 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

There are 702 species in 17 genera. The family contains these genera: * '' Africaniella'' – two species * '' Amblyomma'' – 130 species (includes some of ''Aponomma'') * '' Anomalohimalaya'' – three species * '' Archaeocroton'' – one species * '' Bothriocroton'' – seven species * '' Cosmiomma'' – one species * '' Cornupalpatum'' – one species * '' Compluriscutula'' – one species * '' Dermacentor'' – 34 species (includes ''Anocentor'') * '' Haemaphysalis'' – 166 species * '' Hyalomma'' – 27 species * '' Ixodes'' – 246 species * '' Margaropus'' – three species * '' Nosomma'' – two species * '' Rhipicentor'' – two species * ''

Rhipicephalus ''Rhipicephalus'' is a genus of ticks in the family Ixodidae, the hard ticks, consisting of about 74 or 75 species. Most are native to tropical Africa.Olwoch, J. M., et al. (2007)Climate change and the genus ''Rhipicephalus'' (Acari: Ixodidae) in ...

'' – 82 species (includes ''Boophilus'') * '' Robertsicus'' – one species

Fossil genera

* †'' Compluriscutula'' Poinar and Buckley 2008 Burmese amber, Myanmar,

Cenomanian The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in the s ...

* †'' Cornupalpatum'' Poinar and Brown 2003 Burmese amber, Myanmar, Cenomanian

Medical importance

Many hard ticks are of considerable medical importance, acting as vectors of diseases caused by bacteria, protozoa, and viruses, such as ''

Rickettsia ''Rickettsia'' is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria that may occur in the forms of cocci (0.1 μm in diameter), bacilli (1–4 μm long), or threads (up to about 10 μm long). The term "rickett ...

'' and '' Borrelia''. The saliva of female ticks is toxic, causing

ascending paralysis Paralysis (also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, roughly 1 in 50 ...

in animals and people, known as

tick paralysis Tick paralysis is the only tick-borne disease that is not caused by an infectious organism. The illness is caused by a neurotoxin produced in the tick's salivary gland. After prolonged attachment, the engorged tick transmits the toxin to its host. ...

. Tick species that are commonly associated with tick paralysis are ''

Dermacentor andersoni ''Dermacentor andersoni'', commonly known as the Rocky Mountain wood tick, is a hard tick, or member of the Ixodidae family, with three life stages including larvae, nymph, and finally adult, or, more entomologically, imago. This tick is genera ...

, Dermacentor occidentalis, Dermacentor variabilis,'' and ''

Ixodes holocyclus ''Ixodes holocyclus'', commonly known as the Australian paralysis tick, is one of about 75 species in the Australian tick fauna and is considered the most medically important. It can cause paralysis by injecting neurotoxins into its host. It is u ...

''. Other tick-borne diseases include

Lyme disease Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by the ''Borrelia'' bacterium, which is spread by ticks in the genus ''Ixodes''. The most common sign of infection is an expanding red rash, known as erythema migran ...

babesiosis Babesiosis or piroplasmosis is a malaria-like parasitic disease caused by infection with a eukaryotic parasite in the order Piroplasmida, typically a ''Babesia'' or ''Theileria'', in the phylum Apicomplexa. Human babesiosis transmission via ti ...

, ehrlichiosis, Rocky Mountain spotted fever,

anaplasmosis Anaplasmosis is a tick-borne disease affecting ruminants, dogs, and horses, and is caused by ''Anaplasma'' bacteria. Anaplasmosis is an infectious but not contagious disease. Anaplasmosis can be transmitted through mechanical and biological vector ...

Southern tick-associated rash illness Southern tick-associated rash illness (STARI) is an emerging infectious disease related to Lyme disease that occurs in southeastern and south-central United States. It is spread by tick bites and it was hypothesized that the illness was caused by ...

, tick-borne relapsing fever, tularemia, Colorado tick fever,

Powassan encephalitis Powassan encephalitis, caused by the Powassan virus (POWV), a flavivirus also known as the deer tick virus, is a form of arbovirus infection that results from tick bites. It can occur as a co-infection with Lyme disease since both are transmitte ...

, and Q fever.

References

External links