Pachyseius humeralis Berlese, 1910

Babaeian, Esmaeil, Mašán, Peter & Saboori, Alireza, 2016, The genus Pachyseius Berlese, 1910 in Iran (Acari: Pachylaelapidae), Zootaxa 4088 (3), pp. 420-428 : 426

Pachyseius humeralis Berlese, 1910 [sensu Gholami & Ostovan (2013)]

Pachyseius humeralis is the most common Pachyseius species, showing a wide distribution throughout Europe (Karg, 1993). It was first reported in Iran by Gholami & Ostovan (2013), from edaphic substrates associated with apple trees. They added three photos of the ventral idiosoma (with gnathosoma and legs), ventrianal shield and peritrematal-exopodal scutal complex, respectively, and the following short and vague description to their species (in Persian): idiosoma 580 µm long and 320 µm wide; with separate sternal, genital and ventrianal shields; ventrianal shield 227.5 µm long and 162.5 µm wide, with three pairs of pre-anal setae; three pairs of small platelets (two minute and circular and one larger and elongate) between anterolateral corners of ventrianal shield and peritrematal shields; metapodal shields free and elongate; opisthogastric soft integument with eigth pairs of setae; posterior margin of peritrematal shields and exopodal shields III–IV separate; dorsal setae short and smooth; dorsal shield with punctate-reticulate pattern. Most of these character states are not diagnostic and could refer to many of the known congeneric species. For example, separate sternal, genital and ventrianal shields, and smooth dorsal setae can be found in the Pachyseius species; free and elongate metapodal shields and punctate-reticulate sculpture of the dorsal shield belong to the commonest characters developed in the known species of Pachyseius .

Iranian specimens identified as Pachyseius humeralis are not in good agreement with those as originally described by Berlese (1910) from Italy, and later re-examined by one of us (Mašán, 2007; p. 210). They represent a closely related but distinct species. The specimens from Iran and Europe both have eight pairs of setae placed on soft integument, exopodal shields III–IV separate and not fused to the peritrematal shields, and three pairs of platelets between ventrianal shield and peritrematal shields. However, there are some important differences between them, namely the relative and absolute widths of the idiosoma and ventrianal shield, and the shape of the post-stigmatic section of the peritrematal shields. These differences indicate the incorrect identification of the Iranian specimens. In the specimens from Iran: (1) the idiosoma is more elongated, with length/width ratio 1.81; (2) ventrianal shield is more oblong, 162.5 µm wide, with length/width ratio 1.4; (3) the post-stigmatic section of the peritrematal shields is moderately constricted posterolaterally, with the terminal section narrowed; (4) the exopodal shields are elongated and narrow. In European specimens: (1) the idiosoma length/width ratio is 1.6‒1.75; (2) the ventrianal shield is 165‒235 µm wide, with length/width ratio 1.08‒1.28; (3) the post-stigmatic section of the peritrematal shields lacks a posterolateral constriction, with a convex outer margin, and terminal section relatively wider; (4) the exopodal shields are shorter and wider. These specimens appear to belong to an undescribed species of Pachyseius , but we do not have enough material to allow a full description.