The Parasitiformes is one of thethree major lineages of chelicerate arthropods that are called mites.Ticks are among the most economically important parasitiform mites, butnumerous Mesostigmata, especially in the Dermanyssoidea are alsodebilitating parasites of mammals, birds, and reptiles. The phytoseiidmites used in biological control belong to the Mesostigmata, as do numerousspecies of predators that inhabit soil-litter systems. Currently, both theIxodida (ticks) and Holothyrida consist of three families; the Mesostigmatacontains approximately 70 family-level taxa.
Parasitiform mites have freecoxae, a ventral anal opening covered by a pair of plates, corniculli onthe hypostome (lost in ticks), a sclerotised ring surrounding thegnathosoma (capitulum), and usually a biflagellate tritosternum (lost inticks, many holothyrids, and some parasitic Mesostigmata).
Evolution and Systematics
Discussion of Phylogenetic Relationships
Thehypothesis by Lehtinen (1991) supports a sistergroup relationship betweenHolothyrida and Ixodida; however, other acarologists have suggested thatticks and Mesostigmata are sistergroups. Phylogenetic analyses addressingthe proper placement of ticks are underway in Queensland and Ohio.