Key to females of the world species of Pachyseius
1. Peritrematal shields fused with exopodal shields II–IV or only exopodal shields IV................................. 2
- Peritrematal shields free, not fused with exopodal shields..................................................... 10
2. Dorsal shield bearing 29 pairs of setae, z1 absent............................................................. 3
- Dorsal shield bearing 30 pairs of setae, z1 present............................................................ 4
3. Most dorsal shield setae with expanded spatulate tips, ventri-anal shield with two pairs of setae...................................................................................................... P. cavernicola Ishikawa, 1989
- All dorsal shield setae fine, pointed, needle-like, ventri-anal shield with three pairs of setae........... P. destitutus sp. nov.
4. Anterior margin of sternal shield with a pair of pointed horn-like projections anterior to setae st1 ...................... 5
- Anterior margin of sternal shield straight or curved, but without a pair of horn-like projections........................ 7
5. Opisthogastric soft integument between peritrematal shields and anterolateral margins of ventri-anal shield without any plate-
lets; anterior margin of epistome truncate; small species, length described as 526 Μm...................................................................................................... P. huanrenensis Chen, Bai & Gao, 2009 - Opisthogastric soft integument between peritrematal shields and anterolateral margins of ventri-anal shield with platelets; anterior margin of epistome triangular and pointed; larger species, length more than 600 Μm............................. 6
6. Lateral and opisthogastric soft integument with 11 pairs of setae; anterior margin of epistome not serrated, triangular, without a sharp point; one pair of distinct platelets present between peritrematal shields and anterolateral margins of ventri-anal shield; anterior dorsal shield setae long; j3 longer than distance j3–j4; j4 longer than distance j3–j4; z5 longer than distance z5–z6 ............................................................................ P. sinicus Yin, Lu & Lan, 1986
- Lateral and opisthogastric soft integument with five pairs of setae; anterior margin of epistome serrated, triangular, produced into a sharp point; two pairs of distinct platelets present between peritrematal shields and anterolateral margins of ventri-anal shield; anterior dorsal shield setae short; j3 shorter than distance j3–j4; j4 shorter than distance j3–j4; z5 shorter than distance z5–z6........................................................................ P . chenpengi Ma & Yin, 2000
7. Metasternal plates fused with sternal shield to form a sternal-metasternal complex bearing four pairs of setae........................................................................................ P. morazae Mašán & Mihál, 2007
- Metasternal setae on separate metasternal plates, sternal shield with three pairs of setae.............................. 8
8. Metapodal plates greatly expanded and ornamented, widest anteriorly, their anterior ends abutting exopodal plates IV.......................................................................... P. pachylaelapoides Mašán & Mihál, 2007
- Metapodal plates long and narrow, not greatly expanded, widely separated from ventri-anal and exopodal shields......... 9
9. Pre-sternal shields present; ventri-anal shield with three pairs of setae.................... P. cicaki Mašán & Mihál, 2007
- Pre-sternal shield absent; ventri-anal shield with four pairs of setae.......................... P. quadrigeminus sp. nov.
10. Ventri-anal shield with three pairs of setae................................................................. 11
- Ventri-anal shield with two pairs of setae.................................................................. 16
11. Almost all dorsal shield setae slightly spatulate............................................ P. iraola Moraza, 1993
- All dorsal shield setae fine and needle-like................................................................. 12
12. Pre-sternal area with a pair of well-defined sclerotised pre-sternal plates, clearly separated from sternal shield by a strip of unsclerotised soft skin.................................................... P. crymophilus Mašán & Fenďa, 2014
- Pre-sternal area weakly granulate-reticulate; anterior margin of this weakly sclerotised area may be more distinct, but always connected to sternal shield by an area of granular ornamentation............................................... 13
13. Ventri-anal shield triangular, widest anterior to setae Jv2 ...................................................... 14
- Ventri-anal shield oval-shaped, widest posterior to setae Jv2 ................................................... 15
14. Metapodal shields closely abutting anterolateral margins of ventri-anal shield subequal in length and width (length/width: 0.96–1.07); lateral and ventral soft integument with nine pairs of setae................. P. wideventris Afifi & Nasr, 1984
- Metapodal shields and lateral margins of ventri-anal shield well separated; ventri-anal shield longer than wide (length/width: 1.08–1.28); lateral and ventral soft integument with eight pairs of setae...................... P. humeralis Berlese, 1910
15. Anterior dorsal shield setae short; j3 not long enough to reach j2 or edge of shield, z2 not long enough to reach edge of shield; anterior end of peritreme clearly extending beyond gdj3; ornamentation on ventri-anal shield punctate-lineate over entire shield.................................................................... P. masani Özbek & Halliday, 2014
- Anterior dorsal shield setae long; j3 long enough to reach j2 and edge of shield, z2 long enough to reach edge of shield; anterior end of peritreme level with gdj3; ornamentation on ventri-anal shield very faint or absent in central area of shield............................................................................................ P. slavicus Mašán, 2007
16. Metapodal plates small and oval, fused with and partly enclosed by edges of ventri-anal shield.................................................................................................... P. strandtmanni Solomon, 1982
- Metapodal plates much longer than wide, not fused to ventri-anal shield, posterior ends may be abutting ventri-anal shield. 17
17. Distinct pre-sternal shields present....................................................................... 18
- Distinct pre-sternal shields absent........................................................................ 20
18. Peritrematal shield posteriorly truncated, not expanded at level of stigma; large post-stigmatal pore located posterior to stigma; lateral and opisthogastric soft integument with 19 pairs of setae.................... P. siranensis Özbek & Halliday, 2014
- Peritrematal shield posteriorly not truncated, and expanded at level of stigma; large post-stigmatal pore located lateral to stigma; lateral and opisthogastric soft integument with 11–12 pairs of setae....................................... 19
19. Tarsus II with two spur-like setae, lateral and opisthogastric soft integument with 11 pairs of setae.................................................................................................. P. anisimovi Marchenko, 2015
- Tarsus II with one spur-like setae, lateral and opisthogastric soft integument with 12 pairs of setae.................................................................................................... P. orientalis Nikolsky, 1982
20. Posterior ends of peritrematal shields not reaching posterior level of exopodal plates IV............................. 21
- Posterior ends of peritrematal shields reaching posterior level of exopodal plates IV................................ 22
21. Ventri-anal shield wide anteriorly, narrower posterior to setae Jv2 ............................ P. morenoi Moraza, 1993
- Ventri-anal shield narrow anteriorly, widest posterior to setae Jv2 ...................... P. angustiventris Willmann, 1935
22. Anterior half of ventri-anal shield clearly wider than posterior half, its postero-lateral margins concave; epistome anteriorly narrowed, cone-shaped; tarsus II one spur-like seta....................................... P. friedrichi Mašán, 2008
- Anterior half of ventri-anal shield only slightly wider than posterior half, its lateral margins convex; epistome anteriorly truncated; tarsus II two spur-like setae...................................................... P. angustus Hyatt, 1956