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Main contributors to the taxonomy of Mesostigmata

A large number of acarologists has contributed to the development of the understanding of mite morphology and the subsequent determination of the relationship between the Mesostigmata and other mite groups. In this work we provide a pictorial representation of those that most significantly participated in that process in different parts of the globe, including the deceased as well as representative leading active acarologists ( Figures 6–9 View Figure 6 View Figure 7 View Figure 8 View Figure 9 ). Many of the acarologists currently working in Mesostigmata can be found in the databases cited in Table 8.

A quick inspection of Figures 6–9 View Figure 6 View Figure 7 View Figure 8 View Figure 9 suggests that the early work on systematics of Mesostigmata was dominated by European acarologists. The most influential early contributions came from naturalists in Scandinavian countries, followed by French, then German, Italian, Dutch and British acarologists. Contributions of French, German and Italian acarologists were summarised respectively by Bertrand et al. (2008), Alberti (2005) and Ragusa (2002). North

Americans only became significantly involved in this process in the beginning of the 20th

century, followed by the Russian school and the more recent growth in contributions from

South America, Australia and Africa.

According to Oudemans (1896b), Leach (1815) was the first to propose the establishment of a group of “ Gamasus -like mites” (the present-day Mesostigmata ), which he called

“Gammasides”, consisting of a single genus, Gammasus “ ”. Lists of related names and the corresponding references were presented by Berlese (1892) and Oudemans (1896b). A few years after Leach’s publication, Gamases was used by Dugès (1834a) to refer to a group that he termed “family”, mostly composed of genera currently placed in the Mesostigmata

( Dermanyssus View in CoL , Gamasus , Pteroptus and Uropoda ) as well as Argas View in CoL , which is now placed in the order Ixodida View in CoL . Gervais and van Beneden (1859) presented what they considered to be the nine-member mite groups. Referring to those same groups, Mégnin (1876) called for the need to combine two of them, Gamasides and Ixodides, based on the constitution of the chelicera,

presence of peritreme and location of the respiratory openings. A group composed of the present-day Mesostigmata View in CoL and Ixodida View in CoL was established as the order Mesostigmata View in CoL by Berlese

(1899) and as the suborder Peritremata by Ewing (1913), who also mentioned the closeness of Argas and “ Ixodes ”. Mégnin (1876) also provided detailed characterisations of the genera then included in Gamasides Gamasus (, Pteropus and Uropoda ). Based on the characteristics of the gnathosoma and the first pair of legs, he considered the Uropodina to represent a link, or an evolutive stage, between insects and Arachnida, but that possibility was not fully discussed. Kramer (1881) referred to Gamasidae , a group composed of essentially the same suprageneric taxa mentioned by Dugès (1834a), but not including Argas . Kramer also specified the genera included in the groups previously proposed by Dugès (1834a) and by himself: Pteroptina (with Pteroptus Dufour , a junior synonym of Spinturnix von Heyden ); Uropodina – Trachynotus and Uropodus ; and Gamasina – Dermanyssus , Gamasus and Sejus . Canestrini (1891) was the first to use the name Mesostigmata to designate this order, placing in it the mites with stigmata between the second and third or between the third and fourth coxae.

of the mesostigmatid mites.

At the end of the 1800’s and the beginning of the 1900’s, there were disagreements among acarologists in relation to the existing number of mesostigmatic families. Based on Beaulieu et al. (2011), the first mesostigmatic families (in the present sense of this taxonomic rank) reported in the literature seem to have been Dermanyssidae Kolenati, 1859 ; Uropodidae Kramer, 1881 ; Epicriidae Berlese, 1885 ; Sejidae Berlese, 1885 ; Iphiopsidae Kramer, 1886 ; Laelapidae Canestrini, 1891 ; and Zerconidae Canestrini, 1891.

Canestrini (1891) considered the existence of six families (Demanyssidae; Gamasidae ;

Laelaptidae ; Nicoletiellidae Canestrini, 1891 ; Uropodidae View in CoL ; and Zerconidae View in CoL ). Nicoletiellidae was considered a junior synonym of Labidostommatidae Oudemans, 1904 View in CoL (currently

Trombidiformes View in CoL ) by Bertrand (1990). Berlese (1899) included two groups in the order

Mesostigmata, Gamasida View in CoL and Ixodida View in CoL . In turn, Gamasida was considered to include eight families ( Antennophoridae View in CoL , Celaenopsidae View in CoL , Dermanyssidae View in CoL , Gamasidae , Laelapidae View in CoL , Pteroptidae,

Uropodidae and Zerconidae ) and Ixodida to include two ( Argasidae and Ixodidae ).

Oudemans (1903) considered the Mesostigmata to consist of three families, namely

Parasitidae (then indicated to be a senior synonym of Gamasidae ), Spelaeorhynchidae and

Ixodidae . He considered Parasitidae to contain nine subfamilies, all of which had been considered at the family level by previous authors, and these groups were all once again treated at the family level by Oudemans (1906).

Years later, Vitzthum (1943) considered Laelapidae to consist of 13 subfamilies, most of which had also been considered by other authors at the family level ( Beaulieu et al. 2011).

Trägårdh (1938, 1946) proposed a classification of the Mesostigmata that comprised 13 new families, including new information from the extent and fusion of the plates covering the genital opening. Camin and Gorirossi (1955) extended that idea and established two more families in the suborders Monogynaspida and Trigynaspida , as well as the infraorders Antennophorina and

Cercomegistina View in CoL . More recently, Lindquist et al. (2009) and Beaulieu et al. (2011) moved part of the Monogynaspida View in CoL out to constitute the suborder Sejida Kramer, 1885 View in CoL (originally spelled as

Sejina), as shown in Table 5.

Hence, based mostly on the information provided by Beaulieu et al. (2011), it can be concluded that the major recent changes in the classification of the Mesostigmata included (a)

an increase in the number of superfamilies from one (Parasitoidea) in Banks (1915) to seven

Suborder Sejida Suborder Monogynaspida

Sejoidea Infraorder Uropodina

Heterozerconoidea Microgynioidea

Thinozerconoidea

Suborder Trigynaspida Diarthrophalloidea

Infraorder Cercomegistina Uropodoidea

Cercomegistoidea Infraorder Gamasina

Infraorder Antennophorina Epicrioidea

Aenictequoidea Heatherelloidea

Antennophoroidea Zerconoidea

Celaenopsoidea Arctacaroidea

Fedrizzioidea Parasitoidea

Megisthanoidea Veigaioidea

Paramegistoidea Eviphidoidea

Parantennuloidea Rhodacaroidea

Dermanyssoidea

Ascoidea

Phytoseioidea in Krantz (1978), to ten in Lindquist et al. (2009) ; (b) the addition of numerous new families since the publication of Krantz (1970) – 17 families in Uropodina , 11 in Trigynaspida , one in Rhodacaroidea, one in Zerconoidea, one in Dermanyssoidea and one in Heatherelloidea; (c) the addition of two new families of Ascoidea by Lindquist and Moraza (2014, 2023).

Among key contributors for the understanding of the morphology and or taxonomy of the Mesostigmata, Micherdziński (1966) highlighted the works of H. Vitzthum, A. Berlese, A.C. Oudemans, I. Trägårdh and K. Viets. One should also include A.D. Michael, mostly active in the late 1800’s and early 1900’s, concerning details of the internal morphology (e.g., Michael 1892), as well as N.G. Bregetova, G.O. Evans and E.E. Lindquist. Among the many major contributions of the latter two authors, one should list their contribution to the adoption of chaetotaxy and setal nomenclature, extensively used today for mites of this order (Evans 1963; Lindquist and Evans 1965). Add to that the publications about the Laelapidae mites from the United Kingdom by Evans and Till (1965, 1966, 1979), which established a model for similar publications about mesostigmatic mites in general across the world.

Major contributions were also made by C. Athias-Henriot, including the determination of the variability of the morphology of the spermathecal structures of Mesostigmata , and the possibility of using this information for taxonomic purposes ( Athias-Henriot 1968). A substantial period of time was required from the early report of mesostigmatic spermathecae in the beginning of the 19th century (referred to as “copulatory structure”, by Oudemans 1905) and the detailed study by Athias-Henriot. The contribution of the latter author was also important in the determination of the arrangement of pores and lyrifissures of Mesostigmata ( Athias-Henriot 1975) . Many other prominent acarologists are still making important contributions to the Mesostigmata , but space limitations prevent our discussing them all in detail.