taxonID	type	description	language	source
252BDE551668FFC9D285FF5DFBD1DDA3.taxon	description	Figs. 1 – 3, Table 1	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551668FFC9D285FF5DFBD1DDA3.taxon	materials_examined	Materials examined. Holotype: one female (NSMT-Ap 556), Nishi Park, Chûô-ku, Fukuoka-shi, Fukuoka Prefecture, evergreen broad-leaved forest dominated by Castanopsis sieboldii, 33.5981 º N, 130.3746 º E, elev. 5 m, 18 - VII- 2005, T. Kubota leg. Paratypes: two preimagines (male) (NSMT-Ap 557 – 558), same data as for the holotype. Other materials examined: one maturus junior (NSMT-Ap 559), same data as for the holotype. All specimens including holotype (NSMT-Ap 556) and paratypes (NSMT-Ap 557 – 558) are deposited in NSMT.	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551668FFC9D285FF5DFBD1DDA3.taxon	diagnosis	Diagnosis. Foretarsal sensilla c and d same level with t 2, c closer to d, a’ distal to t 1; P 1 a and P 2 a on thoracic tergites II – III small lanceolate; P 3 on abdominal tergite VI same row with other posterior setae; P 3 a present on abdominal tergites VI – VII; seta P 1 a present on tergite VI.	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551668FFC9D285FF5DFBD1DDA3.taxon	description	Description. Body length 949 μm. Head length 123 μm, width 90 μm; labrum short, 5 μm, LR = 27; cephalic setae l 3, l 5, sd 4, sd 5 short setiform, 5 μm; seta d 6 present; seta sd 7 1.3 times longer than d 7 (Fig. 1 A). Maxillary palpus with two sensilla on penultimate segment, dorsal and ventral sensilla similar in shape and length (Fig. 1 B). Labial palpus reduced to three setae and one sensillum (Fig. 1 C). Canal of maxillary gland simple, proximal part short, CF = 8 (Fig. 1 D). Pseudoculus slightly broader than long, 7 μm x 9 μm, PR = 16 (Fig. 1 E). Pore fp present (Fig. 1 A). Foretarsus (Figs. 2 A – C) 109 μm long; claw 30 μm, TR = 3.6; empodium 3 μm, EU = 0.1. Dorsal sensillum t 1 claviform, almost level with α 3, BS = 0.4; t 2 thin, longer than c and d; t 3 small knob-like, its apex not pointed. Exterior sensillum a surpassing base of d; b longer than c and d; c and d close to each other, subequal in length, situated at same level with t 2; e situated about halfway between γ 3 and α 5, its apex surpassing base of α 7; f at about halfway between e and g, its apex reaching base of γ 5; g at same level with t 3, its apex reaching base of claw. Interior sensillum a' broad, distal to t 1; b' absent; c' not surpassing tarsus. Single pore present between α 3 and a, and between t 3 and g. Seta β 1 sensillum-like, δ 1 – 5 short, δ 5 proximal to δ 4. Middle tarsus 46 μm, its claw 21 μm; hind tarsus 59 μm, its claw 22 μm. Body chaetotaxy as in Table 1 and Figs. 3 A – C. On thoracic tergites II – III (Fig. 3 A), P 1 a and P 2 a lanceolate microchaetae; P 1 a almost halfway between P 1 and P 2; P 2 a slightly nearer to P 3 than to P 2; P 5 a rudimentary; 1 and 2 on thoracic tergite I 33 and 13 μm; P 1, P 1 a and P 2 on thoracic tergite II 33, 3 and 39 μm. Abdominal tergites I – V with three pairs of anterior setae (A 1, A 2, A 5); VI with four pairs (A 1, A 2, A 4, A 5); VII with three pairs (A 2, A 4, A 5) (Fig. 3 B, C). P 3 on abdominal tergites II – V situated anterior to other posterior setae; P 3 on VI – VII in the same row with other posterior setae (Fig. 3 B). Accessory setae, P 1 a, P 2 a and P 4 a, present on abdominal tergites II – VII; P 3 a on VI – VII; these setae short and less than about 1 / 6 of P 1 in length; P 1 a close to P 1; P 2 a near to P 2 (Fig. 3 B, C). Sternite VIII with a single row of four setae (Fig. 3 C). Accessory setae, P 1 a, on abdominal sternites I – VII similar to dorsal accessory setae. P 1, P 1 a and P 2 on abdominal tergite VI 36, 5 and 43 μm; P 1, P 1 a and P 2 on VII 37, 5 and 39 μm. Thoracic tergite II with pores sl and al (Fig. 3 A); III with sl. Pore psm present on abdominal tergites I – VIII, those on VIII without accompanying teeth; psl on VI – VII (Fig. 3 B); al on II – VII (Figs. 3 C, D). Sternites V with two sam; IV – VI with spsm; VII with asymmetrical spsm (Fig. 3 C). Abdominal appendage II – III each with two setae, apical seta less than a half of subapical one (Fig. 1 F). On abdomen VIII, striate band developed, striae distinct (Fig. 3 B, C); comb rectangular with 8 teeth (Fig. 1 G). Female squama genitalis with stout pointed acrostylus (Fig. 1 H). Preimago (male). Body length 780 μm in extended condition. Head length 101 – 105 μm, width 76 μm, LR = 26 – 27, CF = 8 – 9, pseudoculus circular, 8 – 9 μm x 8 – 9 μm, PR = 12 – 13. Foretarsus 86 μm; claw 26 μm, TR = 3.3; empodium 3 μm, EU = 0.1; BS = 0.4. Middle tarsus 38 – 39 μm, its claw 15 – 18 μm; hind tarsus 18 – 20 μm, its claw 18 – 20 μm. Fundamental features almost same with those of imago. P 1, P 1 a and P 2 on thoracic tergite II 21 – 26, 2 – 3 and 33 – 34 μm; P 1, P 1 a and P 2 on abdominal tergite VI 32 – 37, 4 and 35 – 36 μm; P 1, P 1 a and P 2 on VII 32, 4 and 34 – 35 μm. Maturus junior. Body length 533 μm. Head length 103 μm, CF = 10, pseudoculus 7 μm x 7 μm, PR = 14. Fore- tarsus 80 μm; claw 24 μm, TR = 3.4; empodium 3 μm, EU = 0.1. Shape and position of foretarsal sensilla same as those of preceding stages, BS = 0.4. Middle tarsus 35 μm, its claw 14 μm; hind tarsus 40 μm, its claw 19 μm. Seta Mc present instead of M 1 on abdominal tergite VIII and the following setae absent: P 1 a on abdominal tergites II – VI, A 4 on tergite VI, 4 a on tergite IX, 1, 2, and 3 a on tergite X, and 2 and 3 on sternite XI Chaetotaxic variation. Asymmetric absence of A 1 on abdominal tergite VI in maturus junior.	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551668FFC9D285FF5DFBD1DDA3.taxon	discussion	Remarks. The present new species is similar to G. maijiawensis Yin & Imadaté from China in the position of foretarsal sensilla b, c, and d on nearly line, and d close to c, as well as the anterior setae on abdominal tergites II – VII (Yin & Imadaté 1979); however, it differs from G. maijiawensis by the length of foretarsal sensillum a' (long and surpassing δ 3 in G. maijiawensis), the presence of dorsal accessory setae P 3 a on abdomen VI (absent in G. maijiawensis), and the position of P 3 on VI (anterior in G. maijiawensis). This species also resembles G. chichibuensis from Japan and G. shippingensis Yin from China in the shape of the accessory setae on thoracic tergites II – III (small and lanceolate) and the position of P 3 on abdominal tergite VI in same row as the other posterior setae (Nakamura 1995). However, the new species differs from both established species by the setae on the labial palpus (four setae in the two established species), from G. chichibuensis by the position of t 2 (distal to c and d in G. chichibuensis) and P 3 a on abdominal tergite VI (absent in G. chichibuensis), and from G. shippingensis by the chaetotaxy of abdominal tergite VII (eight anterior setae in G. shippingensis) and the position of a’ (almost level with t 1 in G. shippingensis).	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551668FFC9D285FF5DFBD1DDA3.taxon	distribution	Distribution. Japan (Kyushu), known only from the type locality.	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551668FFC9D285FF5DFBD1DDA3.taxon	etymology	Etymology. The species name is derived from the long foretarsus within the genus.	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE55166FFFC5D285FD9DFA3ADB86.taxon	description	Figs. 4 – 7, Table 2	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE55166FFFC5D285FD9DFA3ADB86.taxon	materials_examined	Materials examined. Holotype: female (NSMT-Ap 560), Mt. Koma-ga-take, Kanegasaki-machi, Iwate Prefecture, deciduous broad-leaved forest of Fagus crenata and Clethra barbinervis with herb layer of Sasa kurilensis, 39.185816 º N, 140.934838 º E, elev. 710 m, 18 - VIII- 2001, O. Nakamura et al. leg. Holotype (NSMT-Ap 560) is deposited in NSMT.	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE55166FFFC5D285FD9DFA3ADB86.taxon	diagnosis	Diagnosis. Foretarsal sensilla a – g broad; b subequal to c and d in length, base of c closer to d, f close to e; proximal part of canal of maxillary gland short and large end dilatation; cephalic setae s d 4, sd 5, accessory setae on thoracic segments II – III and abdominal segments I – VII oblong microchaetae. Seta A 4 present on thoracic sternite II. Seta P 1 a absent on tergite VI. Pores lt present on V – VI.	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE55166FFFC5D285FD9DFA3ADB86.taxon	description	Description. Body length 1,079 μm. Head length 148 μm, width 98 μm, labrum not protruded; cephalic setae l 3, l 5 short setiform, 5 and 7 μm, respectively; sd 4 and sd 5 oblong microchaetae (Fig. 4 E), 3 μm; d 6 present; sd 7 1.6 times longer than d 7 (Fig. 4 A). Maxillary palpus with two broad sensilla on penultimate segment, dorsal and ventral sensilla similar to each other in shape and length, 8 μm (Fig. 4 B). Labial palpus with three setae and one sensillum (Fig. 4 C). Canal of maxillary gland simple, proximal part short and stout with large end dilatation (Fig. 4 D). Pseudoculus longer than wide, 12 μm x 9 μm, PR = 13 (Fig. 4 E). Pore fp present (Fig. 4 A) Foretarsus (Figs. 5 A, B) 97 μm, claw 22 μm, TR = 4.5, empodium 3 μm, EU = 0.1. Foretarsal sensilla a – g and a' broad; a, g and a' broader than other sensilla. Dorsal sensillum t 1 claviform, same level with α 3, BS = 0.5; t 2 thin, distal to d; t 3 small knob-like, its apex not pointed. Exterior sensillum a surpassing base of d; b, c, and d on nearly line; b subequal to c and d; c close to d, its apex reaching base of e; d surpassing base of e; e situated about halfway between γ 3 and α 5; f close to e; g at same level with t 3; apices of e, f and g surpassing tarsus. Interior sensillum a' slightly distal to t 1; b' absent; c' linear, its apex reaching base of claw. Single pore present between α 3 and a, and between t 3 and g, respectively. Seta β 1 sensillum-like, δ 1 – 5 short; δ 5 proximal to δ 4. Middle tarsus 36 μm, its claw 19 μm; hind tarsus 42 μm, its claw 20 μm. Body chaetotaxy as in Table 2 and Figs. 6 A – E, 7 A – D. On thoracic tergites II – III (Figs. 6 A, B), P 1 a and P 2 a oblong microchaetae (Fig. 6 C); A 2 and M 2 on sternite I – III short oblong, same as dorsal accessory setae (Fig. 6 D, E). Seven anterior setae (Ac, A 2, A 3, A 4) present on thoracic sternites II – III (Fig. 6 E). 1 and 2 on thoracic tergite I 20 and 13 μm; P 1, 1 a and P 2 on thoracic tergite II 15, 2 and 22 μm. Abdominal tergites I – V with three pairs of anterior setae (A 1, A 2, A 5); VI with four pairs (A 1, A 2, A 4, A 5); VII with three pairs (A 2, A 4, A 5) (Figs. 7 A, B); P 3 on abdominal tergites II – VI situated anterior to other posterior setae (Figs. 7 A, B). Posterior accessory setae on abdominal tergites I – VII oblong microchaetae and less than about 1 / 6 of P 1 in length, but P 1 a absent on VI; P 1 a nearer to P 1 than to P 2; P 2 a near to P 3 (Figs. 7 A, B). P 1 a on abdominal sternites I – VII oblong microchaetae, same as dorsal ones (Fig. 7 D); VIII with a single two of four setae. P 1, P 2 and P 2 a on abdominal tergite VI 20, 25 and 3 μm; P 1, P 1 a and P 2 on VII 24, 3 and 27 μm. Thoracic tergite II – III with pore sl (Fig. 6 A, B). Pore psm present on abdominal tergites I – VIII, those on VIII without accompanying teeth (Fig. 7 C); al on V – VII, lt on V – VI (Fig. 7 D). Sternites V – VII with spsm (Fig. 7 D). Abdominal appendage II – III each with two setae, apical seta about 1 / 3 of subapical one in length (Fig. 4 F). On abdomen VIII, striate band developed, striae distinct (Fig. 7 C); comb rectangular with 7 teeth (Fig. 4 G). Female squama genitalis with stout pointed acrostylus (Fig. 4 H).	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE55166FFFC5D285FD9DFA3ADB86.taxon	discussion	Remarks. The present new species differs from its congeners that are without foretarsal sensillum b’ by the position of foretarsal sensillum f (halfway between e and g in others) and the shape of the accessory setae on abdomen I – VII (normal setae in others). Among the congeners, only in the new species and G. floridanus (Ewing) does foretarsal sensillum b have a subequal length to c and d (Tuxen 1964); however, this new species differs from G. floridanus in the chaetotaxy of abdominal tergites II – VI (eight anterior setae in G. floridanus).	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE55166FFFC5D285FD9DFA3ADB86.taxon	distribution	Distribution. Japan (Honshu), known only from type locality.	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE55166FFFC5D285FD9DFA3ADB86.taxon	etymology	Etymology. The species name is derived from the microchaetae accessory setae on the thorax and abdomen.	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551662FFC2D285FBD4FD37D9B3.taxon	description	Figs. 8 – 9	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551662FFC2D285FBD4FD37D9B3.taxon	materials_examined	Materials examined. Holotype female (NSMT-Ap 78); two females, Shimonada, Futami-cho, Iyo-gun, Ehime Prefecture, 26 - I- 1978, collected by J. Aoki.	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551662FFC2D285FBD4FD37D9B3.taxon	diagnosis	Diagnosis. Foretarsal sensillum t 1 same level with α 3, a’ distal to t 1, e, f and g subequal in length; posterior accessory setae P 1 a and P 2 a on thoracic tergites II – III lanceolate microchaetae, P 3 on abdominal tergites VI – VII same row with other posterior setae. Pores lt present on VI – VII. Supplementary notes on description. Examination of the specimens revealed that some characters needed correction or were omitted in the original description. Cephalic setae l 3, l 5, sd 4, sd 5 short setiform, about 5 μm; seta d 6 present; seta sd 7 1.3 times longer than d 7 (Fig. 8 A); labrum short, 3 μm, LR = 30. Maxillary palpus with two sensilla on penultimate segment, dorsal and ventral sensilla similar to each other in shape and length (Fig. 8 B, C). Pore fp present (Fig. 8 A). On thoracic tergite II – III (Fig. 9 A), P 1 a and P 2 a lanceolate microchaetae; P 1 a halfway between P 1 and P 2; P 2 a near to P 3. Setae P 1 and P 2 on thoracic tergite I 24 and 13 μm; P 1, 1 a and P 2 on II 21 – 23, 2 – 3 and 26 – 27 μm. Posterior principal setae P 3 on abdominal tergites II – V anterior to other posterior ones; but P 3 on VI and VII at same row with other posterior ones (Fig. 9 B). P 1, P 1 a and P 2 on abdominal tergite VI 23 – 25, 4 and 26 – 27 μm; P 1, P 1 a and P 2 on VII 23 – 25, 3 – 4 and 25 – 27 μm. Thoracic tergite II with pores sl and al (Fig. 9 A); III with sl; sternite II with sc posterior to Ac. Pore psm present on abdominal tergites I – VIII (Fig. 9 B), those on VIII with accompanying two teeth (Fig. 9 D); al with II – VI; psl and lt on VI – VII (Figs. 9 B, C). Abdominal sternite IV and VII with asymmetric spsm; V – VI with spsm (Fig. 9 C). Telson with dorsal medial pore with serrate line (Fig. 9 E) and a pair of ventral sal pores at both sides. Notes. The original description states that the principal posterior setae P 3 on abdominal tergite VI are situated anterior to other posterior setae. In the present observation, however, the position of P 3 on VI was in the same row as the other posterior setae. Additionally, in the present study, the posterior accessory setae P 1 a and P 2 a on thoracic tergites II – III were identified as lanceolate microchaetae (though their shape was not mentioned in the original description). The current study revealed that G. aokii shared the following common characteristics with G. macrotarsus sp. nov., G. chichibuensis, and G. shippingensis: lanceolate microchaetae P 1 a and P 2 a on thoracic tergites II – III and the posterior position of P 3 on abdominal tergite VI. Gracilentulus aokii differs from G. macrotarsus sp. nov. by the position of foretarsal sensillum t 2 (distal to c and d in G. aokii) and the presence of P 3 a on abdominal tergite VI (absent in G. aokii). Furthermore, G. aokii differs from both G. chichibuensis and G. shippingensis by the setae on the labial palpus (three setae in G. aokii; four setae in the latter two species). Additionally, it differs from G. chichibuensis by the length of foretarsal sensilla b (surpassing the base of f in G. aokii but not in G. chichibuensis) as well as e and f (neither apex reaching the base of the claw in G. aokii; almost reaching this position in G. chichibuensis), and differs from G. shippingensis in the chaetotaxy of abdominal tergite VII (six and eight anterior setae in G. aokii and G. shippingensis, respectively).	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551662FFC2D285FBD4FD37D9B3.taxon	distribution	Distribution. Japan (Honshu, Shikoku).	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551664FFC1D285F9ADFDA4DD2F.taxon	description	Fig. 10	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551664FFC1D285F9ADFDA4DD2F.taxon	materials_examined	Materials examined. Holotype male (NSMT-Ap 417), allotype female (NSMT-Ap 418), paratype female (NSMT- Ap 420), Mino-yama, Minano-machi, Saitama Prefecture, deciduous broad-leaved forest dominated by Quercus serrata and Acer spp., elev. 500 m, 6 - VI- 1988, O. Nakamura leg.	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551664FFC1D285F9ADFDA4DD2F.taxon	diagnosis	Diagnosis. Labial palpus with four setae; foretarsal sensillum t 1 posterior to α 3; a not surpassing base of c; b not surpassing base of f; posterior accessory setae P 1 a and P 2 a on thoracic tergites II – III lanceolate microchaetae; P 3 on abdominal tergites VI – VII same row with other posterior setae. Supplementary notes on description. Cephalic setae l 3, l 5, sd 4, sd 5 short setiform, about 5 μm; seta d 6 present; seta sd 7 1.3 – 1.7 times longer than d 7; CF = 8 – 9; pore fp present (Fig. 10 A). P 1 a on thoracic tergites II – III halfway between P 1 and P 2; P 2 a near to P 3. 1 and 2 on thoracic tergite I 22 – 25 and 14 μm; P 1, 1 a and P 2 on II 20, 2 – 3 and 24 – 28 μm. P 1 a on abdominal tergites I – VII near to P 1; P 2 a on VI – VII slightly nearer to P 3. P 1, P 1 a and P 2 on abdominal tergite VI 22 – 23, 4 – 5 and 26 – 27 μm; P 1, P 1 a and P 2 on VII 25 – 26, 5 and 26 – 27 μm. Pore psm on abdominal tergite VIII with accompanying teeth (Fig. 10 B). Male squama genitalis with 6 + 6 setae (Fig. 10 C).	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551664FFC1D285F9ADFDA4DD2F.taxon	distribution	Distribution. Japan (Honshu)	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551666FFDAD285FF15FAACDE9F.taxon	description	Figs. 11 – 12, Table 3	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551666FFDAD285FF15FAACDE9F.taxon	materials_examined	Materials examined. 174 females, 39 maturi juniores, 39 larvae II, 1 larva I, botanical garden of Rishiri Town Museum, Senhoushi, Rishiri Island, Hokkaido, mixed forest of Picea jezoensis, Abies sachalinensis, Betula ermanii, Sorbus commixta, 45.113436 º N, 141.216213 º E, elev. 25 m, 18 - X- 2007, M. Sato leg.; 2 females, botanical garden of Hokkaido University, Chûô-ku, Sapporo, Hokkaido, grassland, 43.063456 º N, 141.34378 º E, elev. 20 m, 8 - V- 1980, O. Nakamura leg. 10 specimens (three females (NSMT-Ap 561 – 563), three maturi juniores (NSMT-Ap 564 – 566), three Larvae II (NSMT-Ap 567 – 569), one Larva I (NSMT-Ap 570 )) are deposited in NMST, 10 specimens (four females, three maturi juniores, three larvae II) in the collection of Rishiri Town Museum, and the remaining specimens in the collection of Saitama Museum of Natural History.	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551666FFDAD285FF15FAACDE9F.taxon	diagnosis	Diagnosis. Cephalic setae sd 5 and d 6 absent; foretarsal sensillum b’ posterior to α 4, d at almost same level with t 2; pore lt on abdominal tergite VII situated anteriorly to level of A 5; abdominal tergites II – VI with eight anterior setae; anterior lines of abdominal sternites II – III continuous.	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551666FFDAD285FF15FAACDE9F.taxon	description	Description based on Japanese specimens. Body length 923 μm in extended condition. Head length 103 – 109 μm; width 70 – 76 μm; labrum short, 5 – 6 μm, LR = 17 – 20. Cephalic setae l 3, l 5, sd 4 short setiform, 6 – 7 μm; sd 5 and d 6 absent; d 7 and sd 7 subequal length, 15 – 17 μm (Fig. 11 A). Maxillary palpus with two sensilla on penultimate seg- ment, dorsal sensillum, 9 μm, slightly longer than ventral one, 7 μm (Fig. 11 B). Labial palpus with three setae and one sensillum (Fig. 11 C). Canal of maxillary gland simple (Fig. 11 D), CF = 9 – 11. Pseudoculus circular or slightly broader than long (Fig. 11 E), 7 – 9 μm x 9 μm, PR = 13 – 14. Pore fp present (Fig. 11 A). Foretarsus (Figs. 11 F, G) 72 – 77 μm; claw 24 – 26 μm, TR = 2.9 – 3.1; empodium 3 – 4 μm, EU = 0.1 – 0.2. Dorsal sensillum t 1 claviform, almost same level with α 3, BS = 0.4 – 0.5; t 2 thin, situated at same level with d; t 3 small knob-like. Exterior sensillum a situated between γ 1 and α 3, its apex reaching base of f; b almost same length as c; c almost same level with α 3; d situated at same level with t 2; apices of a, b, c and d each reaching base of f; e situated posterior to α 5; f at about halfway between e and g; g slightly distal to t 3; apices of e, f and g surpassing tarsus. Interior sensillum a' broad, slightly posterior to t 1, its apex surpassing base of b'; b' slightly distal to t 2, its apex not reaching base of c'; c' at same level with α 6, its apex surpassing tarsus. Single pore present near bases of c and t 3, respectively. Setae β 2 sensillum-like; δ 1 – 5 short. Middle tarsus 33 – 35 μm, its claw 14 – 17 μm; hind tarsus 39 – 41 μm, its claw 17 – 18 μm. Body chaetotaxy as in Table 3 and Figs. 12 A – G. On thoracic tergites II – III (Fig. 12 A), P 1 a and P 2 a short setiform; P 1 a halfway between P 1 and P 2; P 2 a slightly nearer to P 3 than to P 2; P 5 a rudimentary. 1 and 2 on thoracic tergite I 27 – 30 and 11 – 13 μm; P 1, P 1 a and P 2 on thoracic tergite II 20 – 25, 5 – 7 and 32 – 33 μm. Abdominal tergites II – VII with four pairs of anterior setae (A 1, A 2, A 4, A 5); but A 1 on VII often asymmetrical absent (Fig. 11 B); P 3 on II – VI situated anterior to other posterior setae (Fig. 11 B); P 1 a on I – VI absent; P 2 a and P 4 a on I – VII and P 1 a on VII short setae, about 1 / 4 of P 1 in length; P 2 a on II – VI nearer to P 2 than to P 3; on VII P 1 a nearer to P 1 than to P 2, P 2 a at middle between P 2 and P 3. Sternite VIII with a single row of four setae; P 1 a on sternites II – VI similar to dorsal ones; P 1 a on VII slightly longer than those on sternites II – VI. P 1, P 2 and accessory setae (P 2 a, P 4 a) on abdominal tergite VI 25 – 26, 30 and 6 – 7 μm; P 1, P 1 a and P 2 on VII 26 – 28, 6 – 7 and 28 μm; P 1 a on sternite VI 6 – 7 μm; one on VII 7 – 8 μm. Thoracic tergite II – III with pore sl (Fig. 11 A). Pore psm present on abdominal tergites I – VIII, those on VIII with accompanying teeth (Fig. 11 C); al on V-VII (Fig. 11 B); lt on VII (Fig. 11 G). Sternite V with spsm; VI with two pairs of spsm; VII with spsm and spm (Fig. 11 G). Abdominal appendage II – III with two setae (Fig. 11 H), apical seta, 5 μm, about 1 / 3 length of subapical one, 14 – 16 μm. On abdomen VIII, striate band developed, striae distinct (Fig. 12 C); comb with about 9 teeth; scattered teeth present on anterior part (Fig. 12 C). Anterior line on abdominal sternites II – III continuous (Fig. 12 D). Female squama genitalis with stout pointed acrostylus (Fig. 11 I). Maturus junior: Body length 656 μm in extended condition. Head length 87 – 92 μm, width 61 – 65 μm, LR = 19 – 28; pseudoculus slightly longer than width or circular, 7 μm x 7 – 8 μm, PR = 12 – 14; CF = 10 – 11; pore fp often invisible. Foretarsus 62 – 65 μm; claw 21 – 23 μm, TR = 2.9 – 3.0; empodium 3 – 4 μm, EU = 0.1 – 0.2. Shape and posi- tion of foretarsal sensilla, and pores same as those of imago, BS = 0.4. Middle tarsus 25 – 28 μm, its claw 15 – 16 μm; hind tarsus 28 – 31 μm, its claw 15 – 18 μm. Body porotaxy almost same as those of imago, but sl on thoracic tergites II – III often invisible; lt on abdomen VII missing. Scattered small teeth present on anterior part on abdomen VIII. Larva II: Body length 611 μm in extended condition. Head length 77 – 86 μm, width 58 – 61 μm, LR = 26 – 32; pseudoculus slightly longer than width or circular, 6 – 7 μm x 7 – 8 μm, PR = 12 – 14; CF = 10 – 12; pore fp missing. Foretarsus 51 – 56 μm; claw 18 – 20 μm, TR = 2.7 – 3.0; empodium 3 – 4 μm, EU = 0.1 – 0.2. Foretarsal sensilla b’ missing, BS = 0.4 – 0.5; pores same as those of preceding stages. Middle tarsus 24 – 28 μm, its claw 13 – 15 μm; hind tarsus 26 – 30 μm, its claw 14 – 15 μm. Pore al present on abdominal tergites I – VII; psm on V – VIII, those on V asymmetric or invisible, those on VIII with accompanying teeth; spsm present on abdominal sternites V – VII, those on V often missing, those on VII often asymmetric. Larva I: Body length 299 μm in compact condition. Head length 76 μm, width 49 μm; rostrum indistinct; pseudoculus slightly longer than width, 7 μm x 5 μm, PR = 12; CF = 12; pore fp absent. Foretarsus 42 μm; claw 18 μm, TR = 2.2; empodium 3 μm, EU = 0.2; BS = 0.4; sensilla b’ and c’ missing; pores absent. Pore psm present on abdominal tergites VII – VIII, those on VIII without accompanying teeth, a pair of ventral pore present at side on telson. Chaetotaxic variation. The chaetotaxy is quite variable and more than one irregularity exists in many specimens. The following anomalies were recorded. Imagines (176 specimens): thoracic tergite I — asymmetric presence of additional P 1 (2 examples), asymmetric absence of P 2 a (1 ex.); thoracic sternite I, presence of additional Ac (2 exs.); thoracic sternite II — presence of additional ventral A 2 (1 ex.); abdominal tergite I — symmetric presence of additional A 2 (1 ex.); abdominal tergite II — absence of A 1 (1 ex.), asymmetric absence of A 2 (1 ex.), asymmetric presence of A 3 (2 ex.), asymmetric absence of A 4 (1 ex.), asymmetric presence of additional A 5 (1 ex.), absence of P 1 (1 ex.), absence of P 2 (1 ex.), asymmetric absence of P 2 a (1 ex.); abdominal tergite III — asymmetric absence of A 4 (5 exs.); abdominal tergite IV — asymmetric absence of A 1 (1 ex.); abdominal tergite V — asymmetric presence of additional A 1 (1 ex.), asymmetric presence of A 3 (1 ex.), asymmetric absence of A 4 (5 exs.), asymmetric absence of P 2 (1 ex.); abdominal tergite VI — asymmetric absence of A 2 (1 ex.), asymmetric presence of A 3 (1 ex.), asymmetric absence of A 4 (4 exs.), asymmetric absence of P 1 and P 2 (1 ex.); abdominal tergite VII — asymmetric absence of A 1 (158 exs.), asymmetric absence of A 2 (2 exs.), asymmetric presence of A 3 (5 exs.); abdominal tergite VIII — absence of M 1 (1 ex.), presence of Mc instead of M 1 (4 exs.), presence of Mc (1 ex.), asymmetric absence of M 2 (1 ex.); abdominal tergite IX — asymmetric absence of 1 (1 ex.), asymmetric presence of additional 1 (1 ex.); abdominal segment X — asymmetric presence of additional 1 (1 ex.); abdominal sternite III — presence of one seta lateroposterior to Ac (2 exs.); abdominal sternite IV — asymmetric presence of A 1 (6 exs.), presence of one seta lateroposterior to Ac (1 ex.), asymmetric presence of P 1 (1 ex.); abdominal sternite V — asymmetric presence of A 1 (3 exs.), presence of A 1 instead of Ac (1 ex.); abdominal sternite VI — asymmetric absence of P 3 (1 ex.); abdominal sternite VII — presence of one seta between A 2 and P 2 (1 ex.), asymmetric absence of P 1 a (1 ex.); abdominal sternite VIII — presence of 5 setae (30 exs.) and 6 setae (1 ex.); abdominal sternite X — asymmetric absence of seta 1 (1 ex.). Maturi juniores (39 specimens): abdominal tergite II — asymmetric presence of A 4 (1 ex.); abdominal tergite III — asymmetric absence of A 1 (2 exs.), asymmetric absence of A 2 (1 ex.): abdominal tergite V — asymmetric absence of A 1 (1 ex.), asymmetric presence of A 4 (1 ex.); abdominal tergite VII — asymmetric (37 exs.) and symmetric (2 exs.) absence of A 1, asymmetric (18 exs.) and symmetric (2 exs.) presence of A 2, asymmetric absence of A 4 (1 ex.); abdominal tergite VII — absence of Mc (1 ex.); abdominal sternite IV — asymmetric absence of P 1 (1 ex.). Larvae II (39 specimens): abdominal sternite II — absence of Pc (1 ex.); abdominal sternite III — absence of Pc (1 ex.); abdominal sternite VIII — asymmetric absence of seta 1 (1 ex.). Notes. Although the Japanese specimens differ slightly from the original description in the length of foretarsal sensilla b and d (neither apex reaching the base of f in the original description) along with b’ (its apex reaching the base of α 6 in the original description), and in the chaetotaxy of abdominal sternite I in larva II (A 2 absent in the original description). However, these differences represent intraspecific variation. Indeed, there are no substantial differences in the important specific features from the original description. This Gracilentulus species belongs to the “ gracilis ” group, which is recorded from Japan for the first time here. Szeptycki (1993) described the anterior setae on abdominal tergite VII as seven setae (Ac, A 2, A 4, and A 5). Since A 1 setae emerge in the maturus junior, their occurrence was confirmed in 176 females and 39 maturi juniores obtained in the current study. In further analysis, a pair of A 1 setae appeared in 18 females while one A 1 had disappeared with high frequency (Table 4). When one A 1 disappeared, the remaining A 1 was found to move slightly toward the center. Hence, seta Ac in Szeptycki (1993) should be A 1; thus, the anterior setae on abdominal tergite VII should be assigned as eight setae in pairs of A 1, A 2, A 4, and A 5, although A 1 disappears asymmetrically with high frequency. Szeptycki (1993) suggested the possibility of facultative parthenogenesis in G. europaeus. In the present study, 176 adults from two sites were all females. Additionally, at Rishiri Island, all larval stages except for prelarva were obtained, indicating that an alternation of generations is taking place here. This result supports the hypothesis of Szeptycki (1993). Both localities from which the species was obtained in Hokkaido were artificial botanical gardens. In Rishiri Island, surveys were conducted at several sites, including natural forests, but the species was only collected in a botanical garden (Maehara et al. 2003; Nakamura et al. 2011). Although proturans have been collected from more than 560 localities in the main island of Hokkaido (Imadaté & Ohnishi 1993), Gracilentulus species had previously not been obtained. Indeed, the current record from the botanical garden in Sapporo is the only locality at which collection has been successful on the main island of Hokkaido. These results suggest that this species was probably introduced into Hokkaido. Similar examples of out-of-country introduction were reported for Proturentomon minimum (Berlese) and Gracilentulus gracilis (Berlese) in New Zealand by Tuxen (1985). In addition, as stated by Minor (2008), the fact that only females were found is also indicative of out-of-country introduction.	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE551666FFDAD285FF15FAACDE9F.taxon	distribution	Distribution. Europe (Poland, France, and Portugal), USA (Delaware), new to Japan (Hokkaido).	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
252BDE55167CFFD9D285F9CFFA21DD16.taxon	discussion	A key to Gracilentulus species by Szeptycki (1993) includes all species known to that time, including those of the “ gracilis ” group (foretarsal sensillum b’ present, b longer than half of c) is currently still available. An updated key to species without sensillum b' on the foretarsus is provided.	en	Nakamura, Osami (2021): The Japanese species of the genus Gracilentulus (Protura: Acerentomidae). Zootaxa 4991 (2): 271-294, DOI: https://doi.org/10.11646/zootaxa.4991.2.3
