Pachyseius subhumeralis, Masan, Peter, 2018

Masan, Peter, 2018, A morphological re-evaluation of Pachyseiushumeralis Berlese, 1910 (Acari, Mesostigmata, Pachylaelapidae), ZooKeys 790, pp. 35-44 : 38-41

Pachyseius subhumeralis sp. n. Figures 2A, 2B, 3B, 4B, 5B, 6B, 7B

Pachyseius humeralis : Hyatt 1956: 4; Karg 1971: 141; Solomon 1982: 102; Lapina 1988: 178; Karg 1993: 116; Mašán 2007: 32, 210.

Material examined.

Type material. Holotype female: Slovakia, Trnavská Pahorkatina Highland, Štefanová Village, Dubník Forest, oak forest (with Quercus spp.), leaf litter and soil detritus, altitude 250 m, June 18, 1997, leg. P. Mašán. Paratypes: 2 females, with the same collection data as in holotype; seven females, Slovakia, Malé Karpaty Mts., Bratislava Capital, Železná Studienka Forest, beech forest (with Fagus sylvatica ), leaf litter and soil detritus, altitude 370 m, April 27, 1993, leg. P. Mašán; 17 females, Bratislava Capital, Devín Settlement, Devínska Kobyla Mt., oak forest (with Quercus spp.), leaf litter and soil detritus; altitude 270 m, July 30, 1997, leg. P. Mašán. All these specimens were previously published as Pachyseius humeralis by Mašán (2007), and are deposited at the Institute of Zoology, Slovak Academy of Sciences, Bratislava.

Non-type material. Bulgaria: one female, Shumen Plateau Natural Park, Shumen City, Bukaka Reserve, old beech forest ( Fagus sylvatica ) with admixed hornbeam ( Carpinus betulus ), leaf litter and soil detritus, altitude 500 m, October 23, 2007, leg. I. Mihál. Czech Republic: two females, with unknown collection data. France: two females, Alpes Cottiennes Mts., Arvieux Village, Gorges du Guil Canyon, pine forest ( Pinus sp.) on a slope with loose rock debris (limestone), humid needle litter with tussocks of grass and mushrooms, altitude 1,180 m, June 11, 2007, leg. P. Fenďa. Germany: three females, Bavaria, Bavarian Prealps Mts., Flintsbach am Inn Village, St. Peter’s Abbey on the Madron ( “Peterskirchlein”), broadleaved deciduous forest predominated by beech ( Fagus sylvatica ), humid soil detritus under a deep layer of leaf-fall, altitude 600 m, April 25, 2007, leg. P. Mašán. Hungary: six females, with unknown collection data. Italy: four females, Lombardy Region, Bergamo Province, Bergamasque Alps and Prealps Mts., Zambla Alta Village, near to Zambla Pass, spruce forest ( Picea abies ) with admixed beech ( Fagus sylvatica ), needle litter and soil detritus with decomposed wood substrate, altitude 1,170 m, May 13, 2015, leg. P. Mašán; three females, Tuscany Region, Florence City, Villa Camerata Hostel, park, broadleaved deciduous wood, leaf litter, altitude 75 m, April 23, 2009, leg. P. Mašán; two females, Florence City, Parco delle Cascine Gardens, broad-leaved deciduous wood, leaf litter with soil and wood detritus, altitude 45 m, May 23, 2006, leg. P. Mašán. Poland: one female, with unknown collection data. Romania: one female, Transylvania Region, Apuseni Mts. (Gilău Mts. in Bihor Massif), Cluj County, Turda Town, Turda Gorge, near to Peştera Ungurească Cave, oak-hornbeam forest, leaf litter, altitude 530 m, July 13, 2006, leg. P. Fenďa. Serbia: three females, Kučajske Planine Mts., Pomoravlje District, Troglan Bara Settlement, Velika Brezovica Forest, beech forest ( Fagus sylvatica ), leaf litter and soil detritus, altitude 900 m, April 23, 2009, leg. I. Mihál. Switzerland: four females, Basel-Stadt Canton, Riehen Town, Wenken Settlement, old beech forest with limes ( Tilia sp.) and maples ( Acer sp.), leaf litter and soil detritus, altitude 380 m, June 1, 2016, leg. P. Mašán. United Kingdom, Wales: two females, Anglesey Island, Llangefni Town, The Dingle Forest, alluvium of Cefni River, mixed broadleaved deciduous forest, leaf litter and soil detritus, altitude 35 m, July 31, 2010, leg. P. Mašán; four females, Anglesey Island, Llandegfan Village, alluvium of Cadnant River, mixed broadleaved deciduous wood, leaf litter and soil detritus, altitude 50 m, July 25, 2010, leg. P. Mašán.

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 in anterior part, transversely striate, separate each other but connected to 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 eight pairs of setae: r6, R2‒R5, ZV2, JV4, and JV5; (7) tarsus II with two subdistal posterolateral setae thickened, of which pl1 with obtuse apex, spur-like, and pl2 terminally attenuate and sharply pointed (but the tip of pl2 is fragile and can be very often broken in slide-mounted specimens); (8) tarsus IV with 17 setae.

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).

There are also less serious differences recognizable between the two compared species, having partly transitional character, for instance in size and proportions of the dorsal and ventroanal shield, and relative length of some idiosomal setae. Generally, when compared with Pachyseius subhumeralis (based on metric data given by Mašán in 2007), Pachyseius humeralis is smaller species (optimum length: 565-595 μm versus 595-640 μm), possessing relatively narrower ventrianal shield (L/W ratio: 1.2‒1.37 versus 1.08‒1.28; Figs 1 and 2), relatively longer setae (j5: 19-25 μm versus 15-23 μm, J5: 31-39 μm versus 24-34 μm), and shallower medial concavity of posterior margin of sternal shield.

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.