A critical historical review of previous classifications and other work on tarsonemid and related mites is presented. General information concerning tarsonemids is reviewed, including the following: geographical distribution, life history, sex determination, sex ratio, copulation, adult female reproductive capacity and longevity, dispersal, food and host preferences, economic importance, and natural enemies.The generic and suprageneric taxa of Tarsonemidae, as known from the world fauna, are revised systematically and phylogenetically, based on a comprehensive assessment of morphology, ontogeny, and homology of tarsonemid structures, including their condition as found in other families of Heterostigmata. The fundamental systems of setal notation developed by Grandjean for the body and appendages of acariform mites are applied, including use for the first time of his special terminology for tarsal setae among heterostigmatic mites.Character transformation series (polarities) for the great majority of characters used in classifying tarsonemid mites are presented for the first time. The out-group method of comparison was used to propose character state polarities, based on the cladistic methodology of Hennig. The transformation series hypothesized for each of 157 characters are numbered, diagrammed in detail, and summarized in tabular form, both for the families of Tarsonemina and Heterostigmata in general and for the genera of Tarsonemidae in particular.Based on the above character transformation series, a tentative phylogeny of the genera of Tarsonemidae is proposed and illustrated by dendrograms. Three subfamilies are recognized, with Pseudotarsonemoidinae new subfam.being the sister-group of [Tarsoneminae + Acarapinae]. Seven tribes are recognized: the sister-groups Pseudotarsonemoidini and Tarsonemellini new tribes in Pseudotarsonemoidinae; the sister-groups Acarapini and Coreitarsonemini in Acarapinae; and sister-groups Steneotarsonemini and Hemitarsonemini new tribes, which together form the sister-group of Tarsonemini, in Tarsoneminae. Similar sister-groupings are proposed for the genera within each tribe, with 31 genera (7 new) and 5 subgenera allotted as follows. Pseudotarsonemoidini:UnunguitarsonemusBeer & Nucifora, 1965;PseudotarsonemoidesVitzthum, 1921;PolyphagotarsonemusBeer & Nucifora, 1965;NasutitarsonemusBeer & Nucifora, 1965; andTarsanonychusnew genus. Tarsonemellini:TarsonemellaHirst, 1923. Coreitarsonemini:AmcortarsonemusFain, 1971;AsiocortarsonemusFain, 1971; andCoreitarsonemusFain, 1970. Acarapini:AcarapisHirst, 1923. Hemitarsonemini:HemitarsonemusEwing, 1939;EotarsonemusDe Leon, 1966; and questionablyHeterotarsonemusSmiley, 1969. Steneotarsonemini:SteneotarsonemusBeer, 1954 (including subgeneraParasteneotarsonemusBeer & Nucifora, 1965, new status;MahunkacarusVainshtein, 1979; andNeosteneotarsonemusTseng & Lo, 1980, new status),Ogmotarsonemusnew genus,Suskianew genus,Phytonemusnew genus,DendroptusKramer, 1876, new status; andAcaronemusLindquist & Smiley, 1978. Tarsonemini:FungitarsonemusCromroy, 1958;RhynchotarsonemusBeer, 1954;Deleonianew genus,CeratotarsonemusDe Leon, 1956;DaidalotarsonemusDe Leon, 1956;IponemusLindquist, 1969;Pseudotarsonemusnew genus;SuctarsonemusMahunka, 1974;XenotarsonemusBeer, 1954;NeotarsonemoidesKaliszewski, 1984; andTarsonemusCanestrini & Fanzago, 1876 (including subgeneraChaetotarsonemusBeer & Nucifora, 1965, new status; andFloridotarsonemusAttiah, 1970,new status). Tribal placement ofPseudacarapisnew genus is uncertain, though it belongs in Tarsoneminae.New generic synonymies include the following:NeotarsonemusSmiley, 1967 objectively underPolyphagotarsonemusBeer & Nucifora, 1965;ParasteneotarsonemusBeer & Nucifora, 1965, andNeosteneotarsonemusTseng & Lo, 1980 subjectively under, but subgenera of,SteneotarsonemusBeer, 1954;PraeacaronemusKaliszewski & Magowski, 1985 subjectively underAcaronemusLindquist & Smiley, 1978;DitarsonemoidesKaliszewski, in prep. subjectively underNeotarsonemoidesKaliszewski, 1984;LupotarsonemusBeer & Nucifora, 1965,MetatarsonemusAttiah, 1970, andCheylotarsonemusTseng & Lo, 1980 subjectively underTarsonemusCanestrini & Fanzago, 1876; andChaetotarsonemusBeer & Nucifora, 1965, andFloridotarsonemusAttiah, 1970 subjectively under, but subgenera of,TarsonemusCanestrini & Fanzago, 1876. Newly designatednomina nudaarePunctatutarsonemusNucifora, 1964, referred toIponemusLindquist, 1969, andLupotarsonemusBeer & Nucifora, 1965, referred toTarsonemusCanestrini & Fanzago, 1876.Descriptions are provided of the subfamily Tarsonemoidea and of all family-group taxa of Tarsonemidae. A key to the adult females, and to the adult males and larvae so far as they are known, together with diagnoses, detailed descriptions, and habitus figures, are presented for the genera and subgenera of Tarsonemidae. Definitions of each genus- and family-group taxon, based primarily on apomorphies, are also given in the section on phylogenetic relationships. Remarks on the distribution, habitats, habits, and other taxonomic and nomenclatorial aspects are given under each genus, followed by a world list of nominate species thought to belong to each genus, and indication of material examined. Descriptions of type-species, either new or inadequately described previously, are given for genera and subgenera as follows:Nasutitarsonemus brontispaeBeer & Nucifora, 1965;Tarsanonychus emblematusn.sp.;Steneotarsonemus(Neosteneotarsonemus)arcticusn.sp.;Ogmotarsonemus erepsisn.sp.;Suskia mansonin.sp.;Pseudotarsonemus eueidesn.sp.;Neotarsonemoides adaeKaliszewski, 1984;Tarsonemus(Floridotarsonemus)scaberAttiah, 1970.Based on transformation series of the same characters mentioned above, a tentative phylogeny of Tarsonemidae and other families of Tarsonemina and Heterostigmata is proposed. A sister-grouping of Tarsonemidae and Podapolipidae is strongly supported apomorphically, with Pyemotoidea being the sister-group of Tarsonemoidea. Pygmephoroidea is strongly supported as the sister-group of [Pyemotoidea + Tarsonemoidea]. Of special note is a series of successive out-group relationships to [Pygmephoroidea + Pyemotoidea + Tarsonemoidea] of Trochometridiidae, then Dolichocybidae, then Heterocheylidae, and finally the Tarsocheylidae as the out-group of all other families of Heterostigmata. Each of the latter four families, therefore, warrants superfamilial status, with Trochometridiidae and Dolichocybidae beingoutsideof Pygmephoroidea and Pyemotoidea, respectively. The Tarsonemina is strongly supported apomorphically as a subcohort. However, Heterocheyloidea appears to represent a sister-group to Tarsonemina rather than to Tarsocheyloidea, such that a grouping of Heterocheyloidea with Tarsocheyloidea, to form a subcohort Tarsocheylina, would be paraphyletic.
