Pachyseius humeralis Berlese, 1910

Masan, Peter, 2018, A morphological re-evaluation of Pachyseiushumeralis Berlese, 1910 (Acari, Mesostigmata, Pachylaelapidae), ZooKeys 790, pp. 35-44 : 37

Pachyseius humeralis Berlese, 1910 Figures 1A, 1B, 3A, 4A, 5A, 6A, 7A

Pachyseius humeralis Berlese, 1910: 255; Berlese 1913: 81; Castagnoli and Pegazzano 1985: 187 (in part).

non Pachyseius humeralis : Nefedov 1966: 1098 (= Pachyseius wideventris Afifi & Nasr, 1984) (a newly introduced misidentification).

Material examined.

Lectotype by present designation: female (slide number 83/5), Italy, Maccarese Village (Rome), humus, labelled as Pachylaelaps humeralis , deposited at the Research Centre for Agrobiology and Pedology, Florence; other specimens: 14 females, Italy, Florence City, Boboli Gardens, leaf litter and soil detritus, May 21, 2006, leg. P. Mašán, deposited at the Institute of Zoology, Slovak Academy of Sciences, Bratislava.

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.

Description.

Female. Dorsal idiosoma. Dorsal shield 540-600 μm long (most frequently 565-595 μm), 320-380 μm wide, suboval, oblong (length/width: 1.6-1.75), widely rounded anteriorly and posteriorly, with almost parallel lateral margins, and delicate reticulation on posterior surface. Dorsal shield with 30 pairs of setae; the setae simple, smooth, needle-like and mostly similar in length; the length of some selected setae as follows: z1 7-10 μm, j1 15-19 μm, j5 19-25 μm, J1 24-28 μm, J2 and J3 27-32 μm, J4 30-36 μm, J5 31-39 μm; the longest dorsal setae 40-48 μm in length. A pair of gland pores gdj3 enlarged, cavity-like, well sclerotized, and situated between setae z1 and z2 close to anterior margin of dorsal shield. Anterior surface with two pairs of minute suboval sclerites situated between setae j2 and j3.

Ventral idiosoma (Figure 1A, B). Presternal area with two platelets (Figure 3A); the platelets free on soft integument, small, subtriangular, with two striae transversely or obliquely oriented on their well sclerotized surface. Sternal shield 112-125 μm long, 76-87 μm wide at the narrowest level of coxae II (120-140 μm at the level of setae st2), with three pairs of subequal setae (st1-st3 36-42 μm), and two pairs of lyrifissures; the shield with anterior and posterior margin almost straight or very slightly concave; sculptural ornamentation well developed, with curved punctate lines on anterior and lateral surface and polygonal or linear pattern of punctations on medial and posterior surface. Two metasternal platelets suboval, each with a seta and pore-like structure. Epigynal shield 110-130 μm long, 74-90 μm wide, oblong, with convex anterior margin, truncate posterior margin, two genital setae, and delicate punctate-reticulate pattern on surface; a row of four suboval and elongate postgenital sclerites along its posterior margin present; genital pore-like structures normally situated on soft integument, outside the shield. Ventrianal shield suboval, longer than wide (length: 218-252 μm, width: 168-198 μm, length/width: 1.2-1.37), with anterior portion moderately expanded, widest anterior to setae JV2, straight or mostly slightly concave anteriorly, widely rounded anterolaterally and posteriorly, bearing lineate-reticulate pattern on entire surface (parallel lines more expressively indicated), three pairs of preanal setae (JV1-JV3), and three circum-anal setae close to suboval anus. Peritrematal shields free from closely adjacent exopodal platelets II–III and III–IV; post-stigmatic sections of the shields narrowed posteriorly, rounded terminally, not reaching beyond the posterior margin of exopodals III–IV, and each bearing three small pore-like structures and one greatly enlarged cavity-like poroid close to stigma. Peritremes normal, with anterior tips reaching marginal dorsal surface between setae z1 and z2, close to enlarged gland pores gdj3 (Figure 6A). Exopodal platelets III–IV free but contiguous to exopodals II–III. Soft integument between peritrematal shields and anterolateral margins of ventrianal shield with two pairs of minute irregular sclerites and a pair of larger suboval platelets. Metapodal region with a pair of narrow, conspicuously elongated and longitudinally oriented platelets; the platelets 52-69 μm long and relatively well separated from anterolateral margins of ventri-anal shield. Lateral and opisthogastric soft integument with seven pairs of setae (Figure 4A): four pairs of dorsomarginal (r6, R2-R4) and three pairs of opisthogastric setae (ZV2, JV4, JV5). All ventrally inserted setae similar to those on dorsal shield.

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).

Legs. Leg setation as previously described in the genus ( Mašán 2007), and for Pachyseius humeralis species group: tarsus IV bearing 17 setae (seta ad2 absent). Tarsus II with two obtuse spur-like distal setae pl1 and pl2 (Figure 5A).

Sperm induction system. Tubiform structures of sperm induction system detectable, weakly sclerotized, long and thin, and associated with posterior margin of coxae III.