Isotogastrura trichaetosa

Description. Body length under slide (n = 4): 0.42 mm (range 0.4 - 0.5 mm), holotype length 0.4 mm. Pale in alcohol, with grey pigmentation uniformly distributed over dorsal areas except for the darker eye patches. Body shape typical of genus, not slender (Fig. 1), without secondary granulation, primary granulation well visible. Head large, with exserted mouth parts as common for the genus (Fig. 2). Ventral side of abdomen wrinkled, especially on manubrium (Fig. 8), which may less visible if the animals are more swollen. Th. I with four dorsal tubercles (Fig. 2). Anterior edge of Abd. V with dorsal glandular opening partly covered by cuticular fold (Fig. 7). One pair of tubercles present at posterior edge of Abd. VI (Fig. 7). Ant. I and II with 7 (rarely 6) and 11 (rarely 12) setae, respectively. Antennal organ of Ant. III with two granulated cuticular papillae, two blade-like inner sensilla, and two outer tubular simple sensilla, one of which is grouped together with inner ones, the other one positioned more proximally and associated with lateral sensillum, which is small and pointed (Fig. 3). Ant. IV with several thin sensilla, two of which are longer. Subapical organite small and strongly depressed. Subapical microsensillum absent or, less probably, shaped as other setae of the segment (Fig. 3). Labrum with 10 setae grouped together at distal edge as in other species of the genus. Two prelabral minute setae (Fig. 2). Maxillary outer lobe with bifurcate (simple in one individual) apical palp and two sublobal hairs. Branch of apical palp well detached from the main part (Fig. 5). Labium with 5 basolateral and 4 basomedian setae. 3 (2) + 3 (2) postlabial setae, posterior pair of setae absent or positioned more laterally. Hypostomal lobe of labial palp well developed, with strong and thick seta H (Fig. 6). Some elements of labial palp difficult to interpret: apical palps of all papillae (A, B, C, D, E) present but reduced and never beyond (normally shorter) associated guards, papilla E smallest. At least 4 proximal setae and 13 guards (possible variation was not studied because limited number of specimens) (Fig. 6). Mandibles slender as typical for the genus. Maxillary head with most lamellae strong and serrated. Head with 4 + 4 ocelli, two inner smaller. Postantennal organ absent. Dorsal chaetotaxy shown is in Figs 2, 7, 8. Th. II-Abd. IV with 3 + 3 axial setae each. Number of sensilla 2, 2 / 1,1,1,1,1, microsensilla absent. Sensilla long, with blunt tips, which distinguished from macrosetae. The leg chaetotaxy of subcoxa 1, subcoxa 2, coxa, trochanter, femur, and tibiotarsus is 1,1,4, 6,11,12; 1,3,7, 6,11,12 and 2,3,8 - 9, 5,10,11 from I to III. Claw and empodium as in Fig. 4, empodium filiform, longer than claw. Thorax without ventral setae. Ventral tube with 6 + 6 lateral paired setae (4 + 4 in distal and 2 + 2 in basal position) and one unpaired posterior seta (Fig. 8). Retinaculum with 3 + 3 teeth, seta absent. Dens with 1 anterio-median and 3 posterior setae. Manubrium without anterior setae. Posterior side of manubrium with 8 + 8 setae; subcoxae furcalis with 5 + 5 setae, (Anterior furcal subcoxa with 5 (6), posterior one with 2 (1) setae) (Fig. 8). Only females known from the material studied.