Megalothorax boerneri sp. nov.

Figs 5–7, 8C, D; Tables 1–2

Material examined. Holotype: female on slide (SMNG-APT-AA00023), France, Haute-Marne, Charmes, 10 Apr. 2011, 47.9262°N, 5.3420°E, mosses growing on a rock, leg. C. Schneider, original collection code: Fr. 021. Paratypes: three females on slides (SMNG-APT-AA0024–26), same data as the holotype. All types deposited in the Apterygota collection of the Senckenberg Museum f̧r Naturkunde G ̂rlitz .

Other material. Two females on slides (SMNG-APT-AA00027, 28), France, Hautes-Pyrénées, Saint-Lary-Soulan, 26 Jun. 2011, 42.8268°N, 0.3114°E, Mosses and litter on the side of a path, leg. C. Schneider, original collection codes: Fr. 031py, Fr. 033py

Molecular data. One individual from Fr.021 (same data as holotype) and one individual from Fr.033py (Genbank accession number in Table 1). Vouchers have not been recovered.

Diagnosis. Colour whitish (in 96 % ethanol), connection of head channels with linea ventralis crossed, without channels on trunk, basomedian fields of labium with 3 + 3 chaetae, basolateral fields of labium with 2 + 2 chaetae, abdomen without β2; but β4 and ζ4 present, abdominal s-chaetae s3 present, only slightly larger than s2, 3 + 3 chaetae on Abd. IV sternite, retinaculum with 4 + 4 teeth, posterior lamellae of the mucro thin and serrated.

Description. General aspect. Habitus and segmentation typical of the genus. Length from labrum to anus: up to 400 µm. Colour whitish (in 96 % ethanol).

Integument. Secondary granulation present dorsally on the head (Fig. 5A), the thoracic region, the abdominal region and Abd. VI sternite (Fig. 7A). Integumentary channels limited to the lateral and posterior part of the head, cycling around the postero-lateral chaetae (Fig. 5A); no anterior channel, connection with linea ventralis crossed. Channels absent on the trunk.

Sensory fields and wax rods. Ordinary distribution of sensory fields and wax rods secretory crypts: 2 + 2 wrc on head, 12 + 12 wrc on body; including the ones associated with the 6 + 6 sensory fields (Fig. 6). Sensory fields include the swollen inner chaetae, all globular: sf1–6: 0, 1, 3, 2, 1, 1. wrc5 and 6 separated from sf5 by ~ 4 granules (Fig. 6).

Head chaetotaxy. Number of chaetae: 12 + 12 in the postero-dorsal region, 10 + 10 and 2 unpaired in the antero-dorsal region, 1 + 1 in the antero-lateral region (Fig. 5A, 8C). With 7 + 7 postero-dorsal chaetae thickened (Fig. 5A), anterior chaetae short and ordinary (Fig. 5A). Ventrally with 3 + 3 post-labial chaetae sub-equally sized.

Labium. Basomedian fields of labium with 3 + 3 chaetae, basolateral fields of labium with 2 + 2 chaetae (Fig. 5B). Labial palps ordinary, as is Fig. 5B.

Labrum. Chaetae a1, a2 with external teeth, a1 with apical outward curvature (Fig. 5C).

Other mouthparts. Oral fold with 2 + 2 chaetae (Fig. 5D). Maxilla outer lobe with two chaetae (apical and basal), sublobal plate with a hair (Fig. 5D). Maxilla and mandibula as in Fig. 5E, F.

Antenna. As in Fig. 5G. Ant. I with one chaeta. Ant. II with four chaetae, the anterior one stronger than the three others. Ant. III with 9 chaetae and the four S-chaetae S1–S4 from the sensory organ; S2 and S3 clearly protruding from the cupule; all S1–S4 rather indistinct in our preparations. Ant. IV with six ordinary chaetae (including X) and 10 + 2 S-chaetae (Sb1–5, Sa1–5, Sx and Sy), Sb3 implanted basally, slightly above S2 and S3 of Ant. III. Organite (Or) small.

Thoracic tergites. As in Fig. 6. Pseudopores and τ-chaetae indistinct, not studied. Th. II with 12 + 12 chaetae and 1 + 1 s-chaetae s1. Th. III with 10 + 10 chaetae, a5 slightly stronger than a6, p4 close to wrc2. Diagram of chaetotaxy provided in Fig. 8D.

Abd. I–V tergites. With 19 + 19 ordinary chaetae, 2 + 2 globular s-chaetae (s2, s3) with s3 slightly bigger than s2; chaetae β2 absent (Figs 6, 8D).

Abd. VI. Tergite with 4 + 4 and 1 unpaired chaetae (Fig. 7A). Each anal valve with one chaeta (Fig. 7A). Sternite with 7 + 7 chaetae, the two axial pairs strongly curvated (Fig. 7A).

Genital plate. Female with 3 + 3 chaetae (Fig. 7A). Male unknown.

Abd. IV sternite. With 2 + 2 usual neosminthuroid chaetae, 3 + 3 ordinary chaetae and 1 + 1 small lobes (Fig. 7A).

Abdominal appendages. Manubrium with 1 + 1 posterior chaetae (Fig. 7B). Dens ordinary, as in Fig. 7B. Mucro with thin lamellae, with ~10–12 teeth on each posterior lamellae (Fig. 7B). Ventral tube with 2 + 2 apical chaetae (Fig. 7C), retinaculum with 4 + 4 distinct teeth.

Legs. Chaetal composition on each legs subcoxa 1, 2, coxa, trochanter, femur and tibiotarsus: leg I—1, 0, 1, 3, 7, 12 chaeta(e) (Fig. 7D); leg II—1, 1, 1, 3, 8 and 12 chaeta(e) (Fig. 7E); leg III—2, 1, 1, 4, 8 and 11 chaeta(e) (Fig. 7F). Claw as in Fig. 7G–J, ordinary, subequal in length. Basal and posterior auxiliary lamellae of unguis well developed, anterior crest indistinct. Basal lobe of unguiculus not or feebly protruding.

Affinities. The most similar species are M. perspicillum, M. incertus sensu nov. and M. laevis . The differential diagnosis is provided in Table 2. Also see the updated interactive key of the Megalothorax species of the world (Schneider 2022).