A morphological re-evaluation of Pachyseiushumeralis Berlese, 1910 (Acari, Mesostigmata, Pachylaelapidae)

Abstract Based on features of the lectotype and newly collected specimens from Italy (Boboli Gardens, Florence), a morphological concept of Pachyseiushumeralis Berlese, 1910 is revised and re-evaluated. New diagnostic character states important for recognition of the species are provided. A misidentified species, formerly widely published in Europe under the name P.humeralis, is established as a new species, Pachyseiussubhumeralissp. n.


Introduction
Pachyseius humeralis was quite briefly and insufficiently described by Berlese in 1910, as the type species of the genus Pachyseius, originally based on female specimens from the two collection sites in Italy (Rome, Mugello). Later in his next paper, Berlese (1913) supported his primary description of the species by adding of some illustrations (ventral idiosoma with gnathosoma, and tarsus II), based on the specimen from Rome (pers. obs.).
Several specimens of Pachyseius humeralis are present in the Berlese Collection, Florence, all from several localities of Central Italy (Maccarese close to Rome, Monte Giovi in Mugello Region, Filettino in Lazio Region, Vallombrosa in Regello Municipality, and Boboli Gardens in Florence), but only two of them (numbered 83/5 and 83/6) belong to the original series of Berlese. In his original description of P. humeralis, Berlese (1910) did not designate a holotype, so his two specimens from "Roma" (83/5) and "Mugello" (83/6) must be considered as syntypes. Mašán (2007) based his revision of P. humeralis upon these two syntypes of which one of them, from Maccarese, Rome, is labelled "tipico" (83/5) by Berlese, and should be considered to be lectotype. Mašán (2007) found that the type specimens examined by him belong to two different species. The lectotype female mounted onto the slide 83/5 was incorrectly considered by him to be identical with the species which was redescribed and illustrated by several authors (Hyatt 1956, Karg 1971, Solomon 1982, Lapina 1988, Mašán 2007. Mašán (2007) overlooked specific morphological differences, described in present paper, between the lectotype and the specimens which were available for his comparative study from Slovakia and other countries in Europe. The paratype female in slide 83/6 was identified as Pachyseius wideventris Afifi & Nasr, 1984 originally described from Netherlands (Afifi and Nasr 1984). The concept of P. humeralis is therefore based on a single specimen, from Rome.
In the Boboli Gardens in Florence, Italy, fourteen specimens of a species which was putatively considered as a new and closely related with Pachyseius humeralis, were collected by me in leaf litter and soil detritus. In order to define the differences between the newly collected specimens and P. humeralis, the lectotype of the species was re-examined. The analysis indicated that my specimens from the Boboli Gardens in Florence were actually clearly conspecific with that on slide number 83/5 of Berlese. So now I can confirm my mistake, and reveal the true identity of P. humeralis sensu Berlese (1910).
The main aim of this study is to diagnose and redescribe the type species of Pachyseius, misinterpreted by the followers of Berlese (1910Berlese ( , 1913, and compare that species with similar but confused species widely reported from various European countries under the name Pachyseius humeralis.

Materials and methods
Collected mites were extracted from the litter and soil detritus by means of a modified Berlese-Tullgren funnel equipped with a 40-Watt bulb, and preserved in ethyl alcohol. Before identification, the mites were mounted onto perma nent microscope slides, using Swan's chloral hydrate mounting medium. A Leica DM 1000 light microscope equipped with a Leica EC3 digital camera was used to obtain measurements and photos. Some multiple images were combined using the CombineZP software program (Hadley 2010). Measurements were made from slide-mounted specimens. Lengths of shields and legs were measured along their midlines, and widths at their widest point (if not otherwise specified in the description). Dorsal setae were measured from the bases of their insertions to their tips. Measurements are mostly presented as ranges (minimum to maximum). The terminology of dorsal and ventral chaetotaxy follows Lindquist and Evans (1965), and that for leg setae follows that of Evans (1963). Identification of pore-like structures on the idiosomal integument is based on the mor-phological observations of Athias-Henriot (1969); notation for these structures such as adenotaxy and poroidotaxy follows Johnston and Moraza (1991).
For the purpose of this study, all the specimens from the large-scale collections so far reported from Slovakia under the confused name Pachyseius humeralis by the author (see Mašán 2007) were checked once again for their correct identity. If available, also specimens recently collected in various European countries were re-examined and listed below. Diagnosis. The species may be distinguished from the other congeners especially by combination of the following female characters: (1) dorsal shield setae simple, needle-like; (2) dorsal shield between setae z1 and z2 and peritrematal shields close to stigma with enlarged and cavity-like poroid structure; (3) presternal platelets well sclerotized, with two striae, separate each other, and free from anterior margin of sternal shield; (4) exopodal platelets II-III and III-IV free, not fused to peritrematal shields; (5) ventrianal shield with three pairs of preanal setae (JV1-JV3); (6) lateral and opisthogastric soft integument with seven pairs of setae: r6, R2-R4, ZV2, JV4, and JV5; (7) tarsus II with two subdistal posterolateral setae thickened, spur-like; (8) tarsus IV with 17 setae.
Gnathosomal structures. Corniculi slender and horn-like; deutosternal groove with four or five transverse rows of denticles and two smooth transverse lines; internal malae reaching beyond the corniculi; gnathosomal setae smooth and needle-like. Palptibia without outgrowths, palptarsus with three-tined apotele. Epistome narrow, with anterior and lateral margin irregularly dentate, apex with larger and pointed central cusp ( Figure 7A).
Sperm induction system. Tubiform structures of sperm induction system detectable, weakly sclerotized, long and thin, and associated with posterior margin of coxae III.
Description. The morphological attributes of the species were described and illustrated in detail by Mašán (2007), and the description does not need to be repeated here. The original illustrations given by the cited author are based on the type specimens from Štefanová Village (see above).
Etymology. Many epithets beginning with sub-, a Latin name-forming prefix meaning "approaching", are intended to distinguish a species from that with which it was previously confused. The new epithet is proposed as an alternative name for Pachyseius humeralis in the broad sense understood to date.
Discussion. The re-evaluation of the lectotype and newly collected material of Pachyseius humeralis sensu Berlese, 1910 showed that there are several apparent and constant morphological differences between this species and its congener widely reported from Europe under the same name, and here established as Pachyseius subhumeralis sp. n. According to these findings, P. humeralis may be most reliably distinguished from P. subhumeralis by the following characters: (1) the placement of genital pores (placed outside the epigynal shield in P. humeralis, or on posterolateral corners of the shield in P. subhumeralis; Figs 1 and 2), (2) the form and placement of presternal platelets (the platelets evenly sclerotized and free on soft integument in P. humeralis, or separately connected to sternal shield with their weakly sclerotized posterior portions in P. subhumeralis; Figure 3), (3) the number of dorsomarginal setae on soft integument (four pairs in P. humeralis -setae R5 absent, or five pairs in P. subhumeralis -setae R5 present; Figure 4), (4) the form of posterolateral seta pl2 on tarsus II (pl2 robust, spur-like, and apically rounded in P. humeralis, or regularly tapered and apically pointed in P. subhumeralis; Figure 5), (5) the relative length of peritremes (the peritreme with anterior tip never reaching beyond the longitudinal axis of gland pore gdj3 in P. humeralis, or reaching slightly beyond this point in P. subhumeralis; Figure 6), (6) the form of epistome (the epistome with narrow base and large central cusp in P. humeralis, or with widened base and uniformly spinate anteriormost margin in P. subhumeralis; Figure 7).
The specimens of Pachyseius humeralis available in the Berlese Collection in Florence from several localities of Central Italy (Monte Giovi, Filettino, Vallombrosa, and Florence), and those from other European regions widely published by various authors (especially from the Mediterranean areas), should be carefully re-examined in the next studies to define their correct identity, and to re-evaluate spatial distribution of the species treated in this paper.