Eosentomon calvum Nakamura, 2010

Nakamura, Osami, 2010, Taxonomic revision of the family Eosentomidae (Hexapoda: Protura) from Japan 2701, Zootaxa 2701, pp. 1-109 : 31-34

Eosentomon calvum Nakamura sp. nov.

Figs. 16–17; Table 6

Type specimens. Holotype female ( NSMT –Ap 465), Sayado, Mouka–shi, Tochigi Prefecture, 36°24'35"N, 140°02'32"E, 90 m elevation, litter from a forest dominated by Quercus myrsinaefolia , Larix leptoleps and Cryptomeria japonica , 7-VI-1997, K. Furuno et al. leg. Paratype: 1 female ( NSMT –Ap 466), same data as for the holotype.

Description. Body length 592 (630) µm. Head 86 (90) µm long, 66 µm wide. Setae aa and pa absent; seta m4 and sensilla as and ps present ( Fig. 16A); seta sp equal to p in length; sensilla pp rudimentary ( Fig. 16F). Labral setae absent ( Fig. 16B). Seta rs simple and longer than sr ( Fig. 16B). On maxillary palpus ( Fig. 16C) sensillum md, 7 µm long, longer than ml, 5 µm. Digits on galea similar to each other in shape and length ( Fig. 16D). Mandible with two teeth ( Fig. 16E). Clypeal apodemes distinct ( Fig. 16B). Pseudoculus with no inner structure ( Fig. 16F), 8 (7) µm long, 5 (7) µm wide, PR = 11.

Foretarsus length ( Figs. 16G, H) 63 (60) µm; claw 14 (15) µm, TR = 4.6 (4.2); empodium 13 µm, EU = 1.0 (0.9); sensillum s slightly longer than claw, 16 (15) µm. Sensillum t1 nearer to α 3 than to α 3', BS = 0.8; t2 slightly spatulate; t3 not surpassing tarsus; a not reaching base of γ 2; b thin; c almost reaching base of γ 3; d reaching base of α 5; e and g spatulate and long; f1 thin, surpassing base of γ 5; f2 shorter than f1; a' reaching nearly to level of x; b'1 absent; b'2 reaching nearly to level of α 6; c' anterior to base of α 6, not reaching base of δ 6. Length of middle tarsus 30 (29) µm, length of claw 8 µm; hind tarsus 37 (36) µm, claw 10 (11) µm; empodia of both tarsi less than 1/10 of claw length ( Fig. 16I), 1 µm long; on hind tarsus ( Fig. 16I) D2 seta-like; D4 spine-like, more slender than D5.

Tracheal camerae distally contracted ( Fig. 17A). Central lobe weak and not observed sufficiently. Laterostigmata II–IV large, II with a central pore, III–IV with no inner structure ( Fig. 17B); those on V–VII small. On female squama genitalis ( Fig. 17C) caput processus thin and bent towards a median edge of stylus, corpus processus dissolved, median sclerotization present. Male unknown

Chaetotaxy as in Table 6. On thoracic tergites II–III, P1a seta-like, slightly longer than P1, posterior to P1–P2 and at nearly halfway between P1 and P2 or slightly nearer to P2 than to P1; P2a seta-like, equal to P 1 in length, at same level with P2–P3 and nearer to P2 than to P3. P1a on abdominal tergite I, P1a and P2a on II–VI, and P2a on VII filiform and longer than P1, at hind margin ( Fig. 17D); P1a on VII sensilla-like, about one-fifth length of P1, posterior to P1–P2 ( Fig. 17D); on tergite VIII ( Fig. 17E) P1a' without basal dilatation and anterior to P2; P2a linear.

Diagnosis. Among Japanese congeneric species except E. tokui Imadaté , this species is characterized by the absence of two cephalic setae, aa and pa. This character places it in the subset named " bohemicum " group by Szeptycki (1985). However,But it differs from the members of the group in the absence of labral setae and the presence of anterior setae on abdominal sternite VIII. The present species is similar to E. tokui from Japan and E. savannahense Bernard from USA ( Imadaté, 1974a, b; Bernard, 1990) in the absence of two cephalic setae, aa and pa, and the presence of anterior setae on abdominal sternite VIII, but it easily distinguished from them by the absence of labral setae (present in other two) and three pairs of setae on sternite IX–X (two pairs in the other two). Moreover, this new species is different from E. tokui in having the pseudoculus without inner structure (two globules in E. tokui ) and the absence of foretarsal sensillum b'1 (present in E. tokui ), and from E. savannahense in five pairs of anterior setae on abdominal tergites II–IV (four pairs in E. savannahense ), two pairs of anterior setae on VII (three pairs in E. savannahense ), and six setae on sternite IX–X (four setae in E. savannahense ).

Chaetotaxic variations observed consisted of the asymmetric presence of A2 on abdominal tergite VII and the asymmetric absence of 2 on abdominal sternite XI of paratype .

Etymology. The specific name is the Latin word meaning “bald” in reference to the lack of cephalic setae aa and pa.

Distribution. Japan (Honshu, known from only the type locality).