Morphology of adult and juvenile instars of Galumna obvia (Acari, Oribatida, Galumnidae), with discussion of its taxonomic status.

The adult instar of the oribatid mite, Galumna obvia (Berlese, 1914), is redescribed in detail, on the basis of specimens from Finland. The morphology of juvenile instars of G. obvia is described and illustrated for the first time, and compared to that of other species of the family Galumnidae. The position of the insertion of the lamellar seta in adults proved variable in studied European populations, being either on or medial to the lamellar line. Since the genera Galumna and Pergalumna are currently distinguished only by the relative positions of the seta and line, specimens of G. obvia in some populations show an intermediate situation between other studied Galumna species - with lamellar seta on or lateral of lamellar line - and Pergalumna with lamellar seta at a distinct distance medially of lamellar line. A detailed reevaluation of the two genera is needed.

Introduction

The oribatid mite PageBreak (Oribatida, Galumnidae) was described by Berlese (1914) as . This species has a semicosmopolitan distribution, being known from the Palearctic and Neotropical regions, i.e. from the USA, South Africa, Santa Elena Islands, Vietnam, and Hawaii (references were summarized by Subías 2004, updated 2013).

The original descriptionand several redescriptions of adult (see below, Taxonomic history) were incomplete, lacking measurements of morphological structures and information about leg setation and solenidia, and morphology of the gnathosoma. Further, lateral and ventral views of the idiosoma, which have important traits in this family, were insufficiently studied and illustrated. The present paper provides a detailed description and illustrations of on the basis of 10 specimens collected in Finland as a reference population. Our data and a literature review show variation in the insertion of lamellar setae, relative to the lamellar line; since this insertion is considered important in distinguishing from , we discuss the generic position of .

Additionally, we described and illustrated the morphology of juvenile instars of . The family Galumnidae comprises more than 450 species, however, the full series of juvenile instars has been studied in detail only for eight species: (Berlese, 1904) (Seniczak et al. 2012), (Jacot, 1935) (Seniczak et al. 2012), (Hermann, 1804) (Seniczak et al. 2012), Grishina, 1982 (Grishina 1982), (Berlese, 1914) (Sengbusch 1954; Seniczak 1972; Grishina 1977; Seniczak et al. 2012), (Berlese, 1914) (Seniczak and Seniczak 2007), Grandjean, 1956 (Seniczak and Seniczak 2007), and (Berlese, 1908) (Seniczak 1972; Seniczak and Seniczak 2007). In addition, Sengbusch (1954) briefly described all juvenile instars of (Jacot, 1929).

Also, the juvenile instars have been described incompletely and/or illustrated in several species briefly, namely: (Grandjean 1935), Bernini, 1984 (Bernini 1984), (Grandjean, 1928) (Grandjean 1928), (Michael 1884), (Jacot, 1929) (Woodring 1965), Woodring, 1965 (Woodring 1965), Oudemans, 1914 (Travé 1970), sp. (Zachvatkin 1953), Wallwork, 1965 (Wallwork 1965), (Cooreman 1941), (Banks, 1895) (Rockett and Woodring 1966), (Grandjean 1956a), (Grandjean, 1933), and (Travé, 1955) (Travé 1955).

Grandjean (1953) summarized the main generic characteristics of juvenile instars of Galumnidae.

Material and methods

Specimens of PageBreak were collected at the following locality: Finland, 64°24'10.78"N, 25°26'7.86"E, Päijänne National Park, Virmailansaari Island, near Padasjoki, 80 m a.s.l., Piceetum vaccinioso-hylocomiosum plant association, moss cover on stones and soil litter, 15.07.2013, collected by Andrei V. Tolstikov. The material collected in the field contained 10 adults, five larvae, two protonymphs and one deutonymph.

Comparative material for the taxonomic discussion originates from one Portuguese and some German locations:

Ribeira de Aljezur, Atlantic coast area of West-Algarve, Portugal, 37.347°N, 8.846°W, floodplain forest, 2011. Weigmann’s collection ();

River Oder Valley, Criewen; North-East Germany, 53.012°N, 14.233°E, moist deciduous forest, 1999. Weigmann’s collection ();

“Berlin 1”; Berlin-Lübars, 52.62°N, 13.37°E, moist meadow, 1986. Weigmann’s collection ();

“Berlin 2”; Postfenn, 52.498°N, 13.24°E, degraded moor, 1997. Weigmann’s collection ();

“Berlin 3”; Berlin-Spandau, Teufelsbruch, 52.579°N, 13.205°E, moor area, 1997. Weigmann’s collection (, );

“Berlin 4”; Berlin-Charlottenburg, 52.5°N, 13.35°E, park forests, 1995. Weigmann’s collection ();

“Oldesloe”; Brenner Moor, near Oldesloe, Schleswig-Holstein, North-West Germany, 53.78°N, 10.33°E, salty moor complex, 1973. Weigmann’s collection ().

Specimens were mounted in lactic acid on temporary cavity slides for measurement and illustration. All body measurements are presented in micrometers. Body length was measured in lateral view, from the tip of the rostrum to the posterior edge of the ventral plate. Notogastral width refers to the maximum width in dorsal aspect. Lengths of body setae were measured in lateral aspect. Formulae for leg setation are given in parentheses according to the sequence trochanter–femur–genu–tibia–tarsus (famulus included). Formulae for leg solenidia are given in square brackets according to the sequence genu–tibia–tarsus. General terminology used in this paper mostly follows that summarized by Grandjean (see Travé and Vachon for references), Weigmann (2006), and Norton and Behan-Pelletier (2009).

Taxonomic history of (Berlese, 1914)

Berlese, 1914: 119, pl. 1: 1. (type locality: Florence, Italy)

: Sellnick 1928 (9); Willmann 1931 (138, fig. 302).

: Zachvatkin 1953 (158, fig. 65); Shaldybina 1975 (353, fig. 887); Mahunka 1992 (246); Mahunka and Mahunka-Papp 1995 (86, 210, fig. 161); Weigmann 2006 (373, fig. 197); Bayartogtokh 2011 (339, fig. 87E).

: Pérez-Iñigo 1993 (77, fig. 25a).

sensu van der Hammen 1952; nec C.L. Koch 1841: Aoki 1966 (774, figs 13–15); Sellnick 1960 (56); Wallwork 1977 (232, fig. 91c).

There is some confusion regarding the validity of , which was declared as junior synonym of (described as Koch, 1841 in CMA 31.5) firstly by Jacot (1929: 4) in the context of the discussion on the type species of Koch, 1835, a question which is not relevant for the synonymy of the species. The original figure of Koch’s shows clearly long interlamellar setae, but the original description of by Berlese (1914, tav. 10: 1) shows clearly very short interlamellar setae, confirmed by the type study of Mahunka (1992) who refered to the redescription of Shaldybina (1975: 353, fig. 887) being in accordance to Berlese’s species. Berlese himself (Berlese 1914: 122, Tav. 10: 7) published his interpretation of (Koch) with the remark that it is different from . Mahunka (1992: 242, fig. 57) figured Koch (sensu Berlese) after a slide in the Berlese collection and declared the specimen in Berlese’s slide 153/29 as lectotype. We follow the interpretations of Mahunka (1992) as did Weigmann (2006) that Koch and Berlese are distinct species. Consequently, the synonymization of with as senior synonym by Jacot (1929) must be rejected. The interpretations of van der Hammen (1952) and others (see above) under the name “” are based on Jacot (1929) and refer to .

Supplementary description of adult

Figs 1–20

Figures 1–8.

, adult: 1 dorsal view 2 ventral view (gnathosoma and legs not shown) 3 anterior part of body, lateral view 4 pteromorph 5 posterior view 6 lamellar seta and parts of lamellar and sublamellar lines 7 sensillus 8 dorso-lateral part of notogaster, lateral view. Scale bars 200 μm (1–3, 5), 100 μm (4), 20 μm (6–8).

Figures 9–20.

, adult: 9 porose area Ad 10 porose area Aa 11 porose area A1 12 porose area A2 13 porose area A3 14 porose area Ap 15 subcapitulum, right half, ventral view 16 palptarsus 17 anterior part of chelicera 18 genital plate, left 19–20 lobes of ovipositor. Scale bars 20 μm (9–14, 16, 19, 20), 50 μm (15, 17, 18).

Measurements. Body length 846–898, width 630–647 (10 specimens, three males and seven females).

Integument. Body color brown to brownish-black. Body surface microfoveolate (well visible under high magnification); foveolae rounded (diameter up to 1) or represented by short lines (on prodorsum and pteromorphs). Posterior part of ventral plate with long, light furrow (f), located posterior and lateral to anal plates. Genital plates with one strong longitudinal fold located medial to genital setae; additional, short, weakly visible folds present in several specimens.

Prodorsum. Rostrum broadly rounded. Rostral (ro) and lamellar (le) setae setiform, barbed. Interlamellar setae (in) short, thin, smooth. Sensilli (ss) long, with weakly developed, elongate, barbed head pointed distally. Exobothridial setae absent. Relative length of prodorsal setae: ss ≈ le > ro > in; measurements given in Table 1. Lamellar (L) and sublamellar (S) lines distinct, parallel. Insertions of lamellar setae located medially to the lamellar lines, very close to them. Porose areas Ad (28–45 × 4–8), transversely oriented, thin, located posterolateral to interlamellar setae.

Table 1.

Comparison of body setae measurements of during ontogeny

Character	Larva	Protonymph	Deutonymph	Adult
	n=5	n=2	n=1	n=10
Length of prodorsal setae:
– rostral setae	53–61	57–61	69	86–98
– lamellar setae	45–53	53–57	61	143–164
– interlamellar setae	32–36	36–45	41	8–12
– sensilli	73–82	77–86	102	143–164
– exobothridial setae	32–36	45–49	45	Absent
Length of gastronotic setae:
– c3	45	45	45	Absent
– h2	20–24	4–6	8	Absent
– p2, p3	Absent	14–16	20	Absent
– other gastronotic setae	4	4–6	8	Absent
Length of epimeral setae	8–12	12–16	16	3b, 3c, 4c (28–36); 1a, 2a, 4a, 4b (12–20)
Length of anogenital setae:
– genital setae	Absent	12–16	16	12–20
– aggenital setae	Absent	Absent	16	8–16
–anal setae	Absent	Absent	Absent	8–16
– adanal setae	Absent	Absent	16	8–16

Notogaster. Anterior notogastral margin well developed. Dorsophragmata (D) of medium size. Notogastral setae represented by 10 pairs of alveoli. Four pairs of porose areas present: Aa (77–131 × 16–32) transversly oriented, elliptical to weakly boot-shaped; A1 (24–57 × 24–32) and A2 (24–53 × 20–28) round or oval; A3 (28–69 × 20–36) oval. All porose areas well visible, but without distinct margins. Alveoli of setae la inserted posterior to Aa. Median pore absent. All lyrifissures distinct; im located anterior to A1. Opisthonotal gland openings (gla) located anterolateral to A2.

Gnathosoma. Subcapitulum longer than wide (188–200 × 172–176). Subcapitular setae (a, m, h) similar in length (28–36), setiform, slightly barbed. Adoral setae (or1, or2) (16–20) setiform, barbed. Palps (147–155) with setation 0–2–1–3–9(+ω); solenidion straight. Chelicerae (225–241) with two setiform, barbed setae; cha (65–73) longer than chb (45–53). Trägårdh’s organ (Tg) distinct, elongate conical.

Epimeral and lateral podosomal regions. Apodemes 1, 2, sejugal and 3 well visible. Seven pairs of setiform, smooth epimeral setae observed; setal formula: 1–1–3–2. Setae 3b, 3c and 4c longer than 1a, 2a, 4a and 4b (Table 1). Discidia (dis) triangular. Circumpedal carinae (cp) distinct.

Anogenital region. Six pairs of genital (g1–g6), one pair of aggenital (ag), two pairs of anal (an1, an2) and three pairs of adanal (ad1–ad3) setae setiform, thin, smooth (Table 1). Anterior edge of genital plates with two setae. Adanal setae ad3 inserted laterally or slightly postero-laterally to lyrifissures iad. Postanal porose area (Ap, 73–110 × 12–24) transversly oriented, oblong. Ovipositor of typical form for Galumnidae (Ermilov 2010): elongate, narrow (327–369 × 65–69); length of lobes 151–164, length of cylindrical distal part 176–205. Each lobes with four thin, smooth setae: ψ1 ≈ τ1 (82–98) longer than ψ2 ≈ τa ≈ τb ≈τc (36–41). Coronal setae k short, thorn-like (12–16).

Legs. Morphology of leg segments, setae and solenidia typical for Galumnidae (Ermilov and Anichkin 2011a, 2011b). Formulae of leg setation and solenidia: I (1–4–3–4–20) [1-2-2], II (1–4–3–4–15) [1-1-2], III (1–2–1–3–15) [1-1-0], IV (1–2–2–3–12) [0-1-0]; homology of setae and solenidia indicated in Table 2.

Table 2.

Leg setation and solenidia of adult

Leg	Trochanter	Femur	Genu	Tibia	Tarsus
I	v’	d, (l), bv’’	(l), v’, σ	(l), (v), φ1, φ2	(ft), (tc), (it), (p), (u), (a), s, (pv), v’, (pl), l’’, e, ω1, ω2
II	v’	d, (l), bv’’	(l), v’, σ	(l), (v), φ	(ft), (tc), (it), (p), (u), (a), s, (pv), ω1, ω2
III	v’	d, ev’	l’, σ	l’, (v), φ	(ft), (tc), (it), (p), (u), (a), s, (pv)
IV	v’	d, ev’	d, l’	l’, (v), φ	ft’’, (tc), (p), (u), (a), s, (pv)

Roman letters refer to normal setae (e to famulus), Greek letters to solenidia. Single prime (’) marks setae on anterior and double prime (’’) setae on posterior side of the given leg segment. Parentheses refer to a pseudosymmetrical setae

Larva, proto- and deutonymph

(Figs 21–30)

Figures 21–24.

, juvenile instars: 21 larva, dorsal view 22 larva, lateral view (gnathosoma and legs except basal parts not shown) 23 deutonymph, dorsal view 24 deutonymph, lateral view (gnathosoma and and legs except basal parts not shown). Scale bars 100 μm (21, 22), 200 μm (23, 24).

Figures 25–33.

, juvenile instars: 25 subcapitulum, right half, ventral view 26 palp 27 chelicera 28 epimeral region of larva 29 epimeral region of protonymph 30 epimeral region of deutonymph 31 anogenital region of larva 32 anogenital region of protonymph 33 anogenital region of deutonymph. Scale bars 20 μm (25–27), 50 μm (28, 29, 31), 100 μm (30, 32, 33).

Dimensions. Length: larva 344–352 (five specimens), protonymph 431, 435 (two specimens), deutonymph 564 (one specimen). Width: larva 246–254, protonymph 332, 336, deutonymph 431.

Integument. Prodorsum, gastronotic shield, gnathosoma and legs light brownish; dorsosejugal and epimeral regions and lateral sides colorless to yellowish. Sclerotized body cuticle microfoveolate (diameter foveolae up to 1); soft dorsosejugal, lateral and anogenital regions region with some folds.

Prodorsum. Relatively short, about 1/2 length of gastronotic region. Rostrum broadly rounded. Rostral, lamellar, interlamellar and exobothridial setae setiform, barbed, inserted on small tubercles. Sensilli with long stalk and weakly developed, lanceolate, barbed head. Relative length of prodorsal setae: ss > ro > le > in ≈ ex; measurements compared in Table 1.

Gastronotic region. Dorsal gastronotic region with large, well-bordered shield (macrosclerite) in all juvenile instars. Transversal gastronotic furrow present (gf), poorly visible. Lateral sides with several small, elongate sclerites (smaller and weakly visible in nymphs than in larva). Larva with 11 pairs of gastronotic setae, proto- and deutonymphs with 15 pairs. Setae c1–c3 and p2–p3 (in deutonymph) on small sclerites. Gastronotic shield with seven pairs of setae (da, dm, dp, la, lm, lp, h1) in larva, 10 pairs (da, dm, dp, la, lm, lp, h1–h3, p1) in proto- and deutonymphs. Gastronotic setae c3 longest, straight, barbed; h2 in larva shorter, setiform, slightly barbed; p2, p3 in proto- and deutonymph setiform, smooth; other setae very short, thin, smooth (Table 1). Porose areas rounded, poorly visible: larva with three pairs (6–8, Aa, A1, A2), proto- (8) and deutonymph (12) with four pairs (A3 present additionally). Cupules ia, im and ip clearly visible. Humeral organ (oh) well developed.

Gnathosoma. Similar to that of adult instar.

Epimeral region. Setal formulae for epimeres: larva 3–1–2 (larval seta 1c scale-like, covering tip of retracted Claparède’s organ); protonymph 3–1–2–1; deutonymph 3–1–2–2. Epimeral setae setiform, smooth (Table 1).

Anogenital region. Ontogenetic genital, aggenital, adanal, anal formulae (larva to deutonymph): 0–1–3, 0–0–1, 0–0–3, 0–0–0, respectively. All setae setiform, thin, smooth (Table 1). Paraproctal setae absent. Cupules ih, ips, iad and opisthonotal gland openings clearly visible, appearing in normal ontogenetic pattern.

Legs. Ontogeny of leg setae and solenidia given in Table 3.

Table 3.

Development of leg setation of during ontogeny.

	Trochanter	Femur	Genu	Tibia	Tarsus
Leg I
Larva	–	d, bv’’	(l), σ	(l), v’, φ1	(ft), (tc), (p), (u), (a), s, (pv), (pl), e, ω1
Protonymph	–	–	–	–	ω2
Deutonymph	–	(l)	–	φ2	–
Leg II
Larva	–	d, bv’’	(l), σ	l’, v’, φ	(ft), (tc), (p), (u), (a), s, (pv), ω1
Protonymph	–	–	–	–	–
Deutonymph	–	l’’	–	l’’	ω2
Leg III
Larva	–	d, ev’	l’, σ	v’, φ	(ft), (tc), (p), (u), (a), s, (pv)
Protonymph	–	–	–	–	–
Deutonymph	v’	–	–	v’’	–
Leg IV
Protonymph	–	–	–	–	ft’’, (p), (u), (pv)
Deutonymph	–	d, ev’	d, l’	v’, φ	(tc), (a), s

See Table 1 for explanations. Setae are listed only for the instar in which they first appear.

Comparison

The adult specimens of collected in Finland correspond to earlier redescriptions (Willmann 1931; Zachvatkin 1953; Aoki 1966; Wallwork 1977; Mahunka 1992; Pérez-Íñigo 1993; Mahunka and Mahunka-Papp 1995; Weigmann 2006; Bayartogtokh 2011) and material in the personal collection of G. Weigmann in terms of general appearance: reatively large body; short, thin interlamellar setae; long, setiform rostral and lamellar setae; sensilli with weakly developed, lanceolate head; four pairs of notogastral porose areas, Aa and Ap being transversely elongate; and short ventral setae. However, the adults from Finland are distinguishable by the presence of a long furrow on the ventral plate, which is not mentioned in other descriptions. We consider this difference as intraspecific variability (perhaps geographical), which should be taken into account in any future identification of this species.

Juvenile instars (larva, proto- and deutonymph) of correspond to those of other Galumnidae in many characters (cf. Michael 1884; Grandjean 1928, 1935, 1953, 1956a; Cooreman 1941; Zachvatkin 1953; Sengbusch 1954; Travé 1955, 1970; Wallwork 1965; Woodring 1965; Rockett and Woodring 1966; Seniczak 1972; Grishina 1977, 1982; Bernini 1984; Seniczak and Seniczak 2007; Seniczak et al. 2012). These include: gastronotum covered by gastronotic shield (macrosclerite); gastronotic setae not on shield inserted on microsclerites; prodorsal setae long or medium size; sensilli long, lanceolate; larva with 11 or 12 pairs (seven pairs inserted on gastronotic shield) and nymphal instars – with 15 pairs (10 pairs inserted on gastronotic shield) of gastronotic setae; gastronotic shield with three (in larva) or four (in nymphal instars) pairs of weakly visible porose areas); humeral organ present; genital formula 0–1–3–5, aggenital formula 0–0–1–1, adanal formula 0–0–3–3, anal formula 0–0–0–2. Juvenile instars of can be distinguished from those of other Galumnidae as follows.

From (, , ) by: the length of prodorsal setae (ro longest in versus in longest in species); length of gastronotic setae of c-series (c3 of medium size, c1 and c2 short, c3 > c1 ≈ c2 in versus c3 and c2 of medium size, c1 short, c3 > c2 > c1 in species); and number of gastronotic setae and length of setae h1 in larval instar (11 pairs – h3 absent, h1 short in versus 12 pairs – h3 present, h1 of medium size in species).

From () by: the length of prodorsal setae (ro longest in versus le longest in ); the length of gastronotic setae of c-serie (c3 of medium size, c1 and c2 short, c3 > c1 ≈ c2 in versus c3 and c2 of medium size, c1 short, c3 > c2 > c1 in ).

From () by: the length of prodorsal setae (ro > le > in in versus in > ro ≈(>) le in ); the length of gastronotic setae of c-serie (c3 of medium size, c1 and c2 short, c3 > c1 ≈ c2 in versus c3 and c2 of medium size, c1 short, c3 ≈ c2 > c1 in ).

From PageBreak species: from by the length of prodorsal setae (ro > le > in in versus in > ro > le in larva, in ≈(>) le > ro in nymphal instars in ), the length of gastronotic setae of c-series (c3 of medium size, c1 and c2 short, c3 > c1 ≈ c2 in versus c3 and c2 of medium size, c1 short, c2 > c3 > c1 in ); from by the length of gastronotic setae (c3 of medium size, c1, c2 and other dorsal setae short, c3 > c1 ≈ c2 in versus c1, c2, c3 and other dorsal setae well developed, of medium size, c1 ≈ c2 ≈c3 in ), and number of gastronotic setae in larval instar (11 pairs – h3 absent in versus 12 pairs – h3 present in ).

From () by: the length of prodorsal setae (ro > le > in in versus le ≈(>) ro > in ); the length of gastronotic setae of c-serie and number of gastronotic setae and length of setae h1 in larval instar (c3 of medium size, c1 and c2 short, c3 > c1 ≈ c2, 11 pairs setae present – h3 absent in versus c3 and c2 of medium size, c1 short, c3 ≈ c2 > c1,12 pairs setae present – h3 present in ).

Thus, the diagnostic morphological characters of Galumnidae juvenile instars are not numerous and can be summarized as: the length of rostral, lamellar and interlamellar setae; the number of gastronotic setae in larval instar; the length of gastronotic setae of c-series, dp, h1; the presence or absence of a transverse furrow on gastronotic shield and genital and adanal macrosclerites on the ventral side in nymphal instars); and body size.

Taxonomic discussion: the position of seta le in species of and

In the Finnish population of , the lamellar seta (le) inserts medial to the lamellar line, at a distance of about 5 µm; no distinct variability is observed. The conventional definition of the genus includes the differential character “lamellar seta on (at) the lamellar line” in contrast to the definition of the genus Grandjean, 1936, originally as subgenus with the differential character “lamellar seta in some distance medially to the lamellar line” (Grandjean 1936; cf. keys of Sellnick 1960, Pérez-Iñigo 1993, Weigmann 2006). Following a strict interpretation of the le position, the Finnish population of could be regarded as a species. To resolve this will require a detailed reevaluation of and a comparison with .

We compared the characters of the Finnish population of PageBreak with those in some other European populations, especially from northwest to northeast of Germany; and we found no convincing character combinations to exclude the Finnish population from , regarding body size (indicated for German populations with 705–845 µm total body length: Weigmann 2006), setation, shapes and positions of porose areas on notogaster, sensillus shape and other characters which are used in literature to define . Concerning the position of setae le relative to the lamellar line, we found remarkable variability. In some populations or specimens, the seta le has some distance, continuously up to 6 µm, in median direction from the lamellar line; in other populations or single specimen le inserts strait at the lamellar line on the median side (cf. Figs 37 and 38): In populations “Oder valley” (n=2) – 0–1 µm, “Berlin 1” (n=3) – 5–6 µm, “Berlin 2” (n=6) – 1–5 µm, “Berlin 3” (n=3) – 0–1 µm, “Oldesloe” (n=6) – 0–4 µm. In all populations we observed a small variability, partly with different ranges. Unfortunately, we have no information about Berlese’s typical population in Italy.

Figures 37–41.

Adults of Galumnidae: 37 , lamellar region of prodorsum, lateral view (specimen from Berlin) 38 , lamellar region of prodorsum, lateral view (specimen from Oder Valley, North-East Germany) 39 , lateral view of prodorsum 40 , lateral view of prodorsum 41 , dorso-frontal view of left part of prodorsum (depressed mounted specimen). Abbreviation: NG– notogastral shield. Scale bar 100 μm.

, juvenile instars: 34 leg I, left, antiaxial view 35 leg II, left, antiaxial view 36 leg III, right, paraxial view. Scale bar 20 μm.

These slight differences of the position of seta PageBreakPageBreakle raise a similar question with regard to other species. Since species descriptions, redescriptions and illustrations are often not sufficiently precise, we give only selective examples. In the type species of , (Hermann, 1804), Grandjean (1936: 97) figured in his very accurate redescription the setae le on the lamellar line. In material of one of the coauthors (G.W.; location “Berlin 3”) of , the insertion of le is a short distance laterally from the lamellar line. The latter position of le is described in several other species, e.g. Grishina, 1981 (Bayartogtokh and Weigmann 2005); Krivolutsky, 1952 (Bayartogtokh and Weigmann 2005); Grandjean, 1956 (Grandjean 1956b: p. 144, 145 as ); Oudemans, 1900 (from three urban sites “Berlin 4”, actually studied within this project); Weigmann 2011 (cf. Fig. 39); Oudemans, 1914 (Travé 1970 from France; actually studied (G.W.) from floodplain forest, South Portugal).

Comparing the position of seta le in strict lateral aspect in (Fig. 40) and in (Figs 6, 37), there seems to be less difference: in both species the seta seems to be inserted a short distance medially from the lamellar line. Yet in dorso-frontal aspect without parallactic error, the distance between le and the lamellar line is about 27 µm in (Fig. 41), in at most 6 µm.

As a preliminary conclusion, most studied species have the seta le inserted a short distance lateral to the lamellar line; in the seta is positioned on the line or lateral to it. is the only species observed with a le insertion medial to the lamellar line or in some specimens on it. The latter two species both show some variability of the le insertion.

The differentiation of the genera and , defined by Grandjean (1936) by means of the insertion of seta le, is called into question by the variable character state in . This single differentiation character is of questionable value to discriminate genera as monophyletic entities, and the character is a simple one with a tendency to variability. Nevertheless, it is convenient to split the - complex in two parts for determination in keys: in “le is inserted on the lamellar line”, in “medially at an obvious distance”. We propose to maintain both genera provisionally until a desirable multifactorial phylogenetic analysis is performed.

An analogous case in the family Malaconothridae relates to the single argument to differentiate Berlese, 1904 from Berlese, 1916, by the typological characters “monodactylous or tridactylous legs”. This character state is easy to distinguish but obviously without phylogenetical value. Colloff and Cameron (2013) provided a multifactorial analysis for several species of both genera. They found no reasonable pattern to confirm either genera as monophyletic: as a result was considered a junior synonym; and Knülle, 1957, could be established as valid taxa without the number of claws being a key character.