Tolmerinus fratrumelliotorum Rougemont, 2017

Hu, Fang-Shuo, Solodovnikov, Alexey & Fikáček, Martin, 2025, The larva of the genus Tolmerinus Bernhauer described: does it help to reveal a sister-group for the rove beetle subtribe Anisolinina (Coleoptera: Staphylinidae: Staphylininae)?, Arthropod Systematics & Phylogeny 83, pp. 369-389 : 369-389

3.2. Larval description for Tolmerinus fratrumelliotorum Rougemont, 2017

Figures 1 , 2 , 3 , 4 , 5 , 6

Material examined.

TAIWAN: Kaohsiung City: Altogether the examined material includes eighteen larvae (three specimens of L 1, thirteen specimens of L 2 and two specimens of L 3) and eight adults as follows: 5 adults (3 males and 2 females), Zuoying district (左營區), Banpingshan (半屏山), SW slope, 100 m, 22.694262, 120.305072, 9-22.vii.2021, M. Fikáček lgt. by squid-baited pitfall traps, TW 2021-06 d ( FSHC, NMNS, NHMD) ; L 2, 1 spec.; 3 female adults, Zuoying district (左營區), Banpingshan (半屏山), SW slope, 100 m, 22.694296, 120.305797, 22.vii.2021, M. Fikáček lgt. by sifting leaf litters, TW 2021-06 e ( NHMD) ; L 1, 1 spec., L 2, 3 spec., L 3, 1 spec., same locality as the previous one, 30.v.2023, BP 8 ( NHMD) ; L 2, 3 spec.; L 1, 1 spec., Zuoying district (左營區), Banpingshan (半屏山), SW slope, 90 m, 22.693469, 120.304979, 13.vi.2021, M. Fikáček lgt. by sifting leaf litters, TW 2021-06 ( NHMD) ; L 1, 1 spec., L 2, 2 spec., same locality as the previous one, 30.v.2023, BP 10 ( NHMD) . Nantou County: L 1, 1 spec., Huisun Forest reserve, track to Xiaochushan Mt. , 24.0744602 N, 121.0366337 E, 1150 m, 16.viii.2021, Fikáček & Liang lgt. by sifting leaf litters, 21-08 - HS 1 ( NHMD) ; L 3, 1 spec., same locality and date as previous one, 21-08 HS 1001-1 (extracted voucher, FS 026 L) ( NHMD) ; L 2, 1 spec., same locality and date as previous one, 21-08 HS 1001-2 ( NHMD) ; L 1, 1 spec., Huisun Forest res., Wading trail , 24.0892139 N, 121.0297836 E, 700 m, 17.viii.2021; Fikáček & Liang lgt. by sifting leaf litters ( NHMD) . Taichung City: L 2, 3 spec., Wufeng, Beikeng Creek trail 24.045 120.7827, 410 m, 24 May 2023, FS Hu, YJ Chen, TW 2023-018, lowland tropical forest with large accumulation of leaf litter and sparse understory, Taiwan Leaf Litter Beetles Project Additional specimens, WF 1-08 ( NHMD) .

Description of the third instar larva (L 3).

Measurements (in mm, n = 2): Body length: 12.21 (11.83–12.73); head width (HW): 1.43 (1.35–1.49); head length: 1.48 (1.38–1.53); pronotum width: 1.34 (1.27–1.42); pronotum length: 1.42 (1.33–1.52). — Habitus: Body slender, with relatively large head and long, slender legs, prothorax slightly wider than head, gradually wider posteriorly, mesothorax and metathorax slightly wider than prothorax and abdominal segments. Color: head and pronotum dark yellowish-brown, mandibles darker, thorax gradually darkening from mesonotum to metanotum, abdominal tergites I – IX same as metanotum, abdominal sternites I – IX yellowish-brown. Antennae, maxillae, labium light yellowish-brown. Basal part of urogomphi and abdominal tergite and sternite X dark brown but slightly lighter than abdominal tergites I – X, apical part of urogomphi yellowish-brown. — Head: Head capsule weakly transverse, slightly expanded from base anteriad, widest at stemmata level, with distinct pair of epicranial glands. Neck presents as distinct carina-delimited constriction. Each side of head with 4 pigmented stemmata in cluster, anterior two similar in size, slightly larger than upper-posterior one; lower-posterior one indistinct, almost indistinctive. Epicranium with five pairs of macro and five pairs of micro setae located symmetrically, divided by dorsal ecdysial line, two pairs of small pores located before epicranial dorsal setae, three pairs of posterior setae and one pair of posterior pores on posterior area; head chaetotaxy as in Fig. 3 A . Nasale (Fig. 3 C ) with one pair of glandular pit and olfactory organs (Fl 1), anterior margin of nasale with nine teeth, median tooth short, at same level as lateral teeth one, paramedian teeth longer than other teeth, lateral teeth two slightly shorter than paramedian teeth but longer than lateral teeth one and two, lateral teeth three short, slightly expanding to outer margin; setation on teeth symmetrical, with nine to ten pairs of macro setae and two to three pairs of micro setae. Head ventrally with 5 pairs of macro and 3 pairs of micro setae located symmetrically, divided by ventral ecdysial suture (Fig. 3 B ). Apotome triangular, both sides anteriorly membranous, median part sclerotized, with narrow and long stalk extending beyond tentorial pits; one pair of macro setae in front of stalk, two pairs of micro setae anteriorly. Tentorial pits large and oval. Ventral ecdysial line with small median spindle-shaped sclerite near its middle. Antennae four-segmented, slender; segment I cylindrical, shorter than other segments; segment II longer than segment III, slightly swelled in anterior part; segment III longer than segment IV, distinctly swelled in middle of its inner part; segment IV more slender than other segments, slightly longer than segment I, membranous apically, with three solenidia in one cluster; segment II with three macro setae; segment III with three macro setae and with apically pointed sensory appendage, with one small pore in its inner part near sensory appendage, with one solenidium behind small pore (Fig. 4 D ). Mandibles slender, apically blunt, with one seta externally at base, two campaniform sensilla dorsally of which one located in 1 / 3 base of mandible in middle, another located in 1 / 2 from base at external margin; with one campaniform sensillum ventrally, located in 1 / 2 from base in middle (Fig. 4 B ). Maxillae with cardo slightly shorter than stipes, about 1.5 times wider than stipes, with one seta in anterior part of outer margin; stipes with nine setae, one on outer margin in middle distinctly longer than others, one near distinctly longer seta, two located near base of outer margin, two near middle of inner margin, another three evenly dispersed along with anterior part of inner margin; mala digitiform, slender and long, with two setae dorsally, one near base of inner margin, one near middle of outer margin, four solenidia in one cluster apically; palpifer with one seta dorsally, near inner margin; maxillary palps four-segmented, segments I, II and III almost equally wide, segment IV slightly narrower; segment II distinctly longer than others, segment III slightly longer than segment I, segment IV fusiform, shorter than other segments; segment II with two setae, one near middle of inner margin, another located in anterior part of outer margin, segment III with one pore, located near base of outer margin (Fig. 4 A ). Labium with well-sclerotized ventral side of prementum, slightly membranous anteriorly, with pair of setae apically located on anterior margin of well-sclerotized part; labial palps three-segmented, segment I distinctly longer and wider than segments II and III, segment II longer than segment III, segment III fusiform, shorter than other segments; ligula very long, can be divided into two halves, one half sclerotized with one pair setae in anterior part of outer margin, another half membranous with seven solenidia separated apically (Fig. 4 C ). — Thorax: Prothorax longer than wide, meso- and metathorax wider than long, mesothorax slightly longer than metathorax; protergite with posterior carina, meso- and metatergite with anterior and posterior carinae. Thorax dorsally with mid-longitudinal ecdysial line. Thorax with simple macro or micro setae, without frayed setae (except on legs); chaetotaxy of pro-, meso-, and metanotum as shown in Fig. 5 A . Cervicosternum large, triangular, with four pairs setae, two pairs near anterior suture of cervicosternum, one pair in middle of cervicosternum near ecdysial line, one pair on its posterior margin. Sternite of prosternal area trapezoid; with pair of setae near anterior margin (Fig. 5 B ). Spiracle oval. Legs (Fig. 5 F ) long and relatively slender; fore femora with about 22 spine-shaped setae, with longitudinal furrow medially, seven pairs of setae located along this furrow; foretibia with about 18 spine-shaped setae, 15 bifid setae located from its middle to anterior part in form of two or three clusters; tarsungulus with three spine-shaped setae (Figs 5 C – D ). — Abdomen: Abdominal segments with visible dark sclerites, with large or small frayed setae and long or short simple setae. Segment I with pair of paratergites and parasternites fused to each other. Segments II – VIII with pair of paratergites and pair of parasternites (Fig. 5 D ). Sternite I strongly reduced and of irregular shape, less sclerotized than other segments (Fig. 5 E ). Chaetotaxy of segment I simpler than more even serially homologous chaetotaxy on segments II – VIII (Fig. 5 C – E ). Segment IX with reduced chaetotaxy, without laterosclerites or ecdysial line. Segment X (pygopod) with about 24 relatively short spine-shaped setae dorsally and 16 relatively long spine-shaped setae ventrally, all setae located asymmetrically (Figs 6 A – B ). Urogomphi likely two-segmented (no complete specimen of mature larvae, the segmentation is inferred from early instars only), very long, at least four times as long as abdominal segment IX; first half of segment I straight, with about 30 relatively short setae; second half of segment II formed at least by eight cylindrical pseudosegments, each bearing three very long setae, these setae becoming gradually longer from base to apex of the segment (Fig. 6 C ).

The difference between larval instars.

Measurements for the first instar larva (L 1) (in mm, n = 5): Body length: 5.73 (5.24–6.29); head width (HW): 0.94 (0.92–0.98); head length: 0.77 (0.67–0.83); pronotum width: 0.91 (0.86–0.94); pronotum length: 0.67 (0.64–0.68). — Measurements for the second instar larva (L 2) (in mm, n = 11): Body length: 6.83 (6.10–7.38); head width (HW): 1.01 (0.93–1.05); head length: 0.91 (0.80–1.00); pronotum width: 0.84 (0.78–0.91); pronotum length: 0.86 (0.82–0.92).

L 3 (see measurements above in the description) is larger than L 1 and L 2. The whole body of L 1 is pale-yellow and less sclerotized than in L 2 and L 3. Habitus of L 2 is similar to L 3. Mandibles in L 1 are relatively sharper and more sclerotized in the apical half of mandibles than in L 2 and L 3. Apotome stalk absent in L 1, but present in L 2 and L 3; ventral ecdysial lines of L 1 very short without median spindle-shaped hole, L 2 and L 3 with median spindle-shaped hole on the second half of ecdysial line. The bifid setae of foretibia present in L 2 and L 3 but absent in L 1. Tarsungulus with only two spines in L 1, but three spines in L 2 and L 3.

Biology.

Adults and larvae of Tolmerinus fratrumelliotorum were collected together from various habitats. In secondary forests with Ficus , they were found using squid-baited pitfall traps. In karst areas, they were collected by sifting through shallow leaf litter accumulations, which often included wood debris, fungi, and fallen fig fruits. In primary forests on slopes with sparse understory, the species was located by sifting through leaf litter accumulations, which may also contain fungi and mammal excrement. Additionally, the species was collected from small leaf litter accumulations in stony forests on mountain slopes. Interestingly, three sequenced specimens of T. fratrumelliotorum were contaminated by DNA of Burmaniscus isopods, which may indicate that Tolmerinus adults and larvae prey on terrestrial isopods.

Distribution.

Tolmerinus fratrumelliotorum is known from the type specimens collected in Hong Kong, China ( Rougemont 2017) and is now reported from Taiwan for the first time. Our data indicates that it may be widespread in Taiwan.

Remarks.

Matějíček and Boháč (2020) indicated T. auronotatus Fauvel, 1895 to occur in Taiwan, based on the catalogue of Herman (2001). However, Herman (2001) only listed the species for Myanmar. Therefore, Tolmerinus fratrumelliotorum is at the moment the only species of the genus known in Taiwan. Additional species of Tolmerinus were collected by us during the Taiwanese Leaf Litter Beetles Barcoding project ( Hu et al. 2024). The identifications of these species will be published in future papers.

Figures

Figure 1. The habitus and aedeagus of adult Tolmerinus fratrumelliotorum. A: Habitus; B, D: aedeagus in parameral view. C: aedeagus in lateral view. Scale bars: 0.5 mm.

Figure 2. Habitus of first and third instars of larvae of Tolmerinus fratrumelliotorum. A: first instar. B: third instar. Scale bars: A, 1 mm; B, 2 mm.

Figure 3. Head and nasale of the third instar larva of Tolmerinus fratrumelliotorum. A: head in dorsal view. B: head in ventral view. C: nasale in dorsal view. Scale bars A, B: 0.5 mm; C: 0.2 mm. Abbrevations: Ap, apotome. Des, dorsal ecdysial suture. E, epicranial part. Ed, epicranialodorsal seta. Em, epicranial alomarginal seta. Ep, epicranial pore. Fl, frontal lateral seta. Fm, frontal marginal seta. Gp, glandular pit. L, lateral; Lt, lateral teeth. Mt, median tooth. Na, nasale. P, posterior part. Pmt, paramedian tooth. Pp, posterior pore. Tp, tentorial pit. V, ventral part. Ves, ventral ecdysial suture. Vl, ventrolateral seta. Vm, ventral marginal seta.

Figure 4. Head appendages of the third instar larva of Tolmerinus fratrumelliotorum in dorsal view. A: maxillary palps. B: mandible. C: labium. D: antenna. Scale bar: 0.2 mm. Abbrevations: Cd, cardo. Cs, dorsal sensillum. Lg, ligula. Ma, mala. Pf, palpifer. Pmn, prementum. Sa, sensory appendage. St, stipes.

Figure 5. Thorax, forelegs and abdominal segments I and II of the third instar larva of Tolmerinus fratrumelliotorum. A: thorax, in dorsal view. B: prothorax, in ventral view. C: abdominal segments I and II, dorsal view. D: same in lateral view proleg, in latero-ventral view. E: same in ventral view. Scale bars: A, 1 mm; B-E, 0.5 mm. Abbrevations: Cc, coxal cavity. Cr, cervicosternum. Fe, femora. Pro, prothorax. Meso, mesothorax. Meta, metathorax. Sn, sternite. Sp, spiracle. Tb, tibia. Tr, trochanter. Tu, tarsungulus.

Figure 6. Abdominal segments IX and X of the first and third instars larva of Tolmerinus fratrumelliotorum. A: abdominal segments IX and X of third instar, in dorsal view. B: same in ventral view. C: same structures of first instar, in lateral view. Scale bars: 1 mm. Abbreviations: Ugl: urogomphi.