Thalerosphyrus bengalensis Vasanth, Kubendran & Subramanian 2025, sp. nov.

Thalerosphyrus bengalensis Vasanth, Kubendran & Subramanian sp. nov. (Figs 1–50) Material examined. Holotype. Mature larva, INDIA, West Bengal, Purulia district, Jalika village stream, 23.41131°N, 86.19734°E, 311 m. 14.X.2022, coll. T. Kubendran (Reg. no. I/E/864). Paratypes: 15 larvae, same place and data as holotype (Reg. no. I/E/865) Description. Mature larva. (Fig.1). Length (mm): body 13–14; cerci 9.5–10.5; head length 1.5–2; head width 3.3–3.5; prothorax width 3.5–4 (Fig. 25). Colour. Generally brownish with pale white (Fig. 1). Antennae are pale brown and very short (Fig. 5). Head sub quadrangular, brown with pale dots, and flattened; anterior margin of head with numerous small setae; dorsal surface with four pale dots; ocelli with three black dots mixed with pale colour in the middle (Figs 1–5). Head. Mouthparts: Labrum expanded laterally, 4.5× wider than long, anterior margin straight, medially bulged with a concave shape and small blunt crenations on either side (Figs 12–14), dorsal surface with a curved row composed of 10–11 long stout setae (Fig. 14); dorsal surface and anterior margin covered with long, hair-like and stout setae; ventral surface of anterior margin with numerous long setae. Mandibles slightly bent in distal part; anterolateral margins with two rows of dense long hair-like setae; anterolateral margins with median bulge. Right mandible with two outer incisors broad with serrations on the inner margin, composed of 7 blunt teeth; inner incisor with two blunt teeth; prostheca with 6–7 thick setae surrounded with small setae; mola joined, posterior margin with 5–6 hair-like setae (Figs 16–17). Left mandible with single outer incisor serrated with 6 blunt teeth; inner incisor with two blunt teeth, anterior teeth smaller than posterior; prostheca with 8 thick fimbriate submarginal setae; mola with 7–8 setae and posterior median margin with 5 hair-like setae (Figs 18–19). Maxilla with long, simple setae on inner margin on the lateral margin and dorsal surface with stout setae. Segment I of maxillary palp on dorsal surface proximally with numerous long thread-like setae and rows of thin and simple setae on outer margin; segment II long and apically broad with rows of numerous long hair-like setae on outer margin; apical segment small, pointed, with rows of simple setae on outer margin. Crown of the galea-lacinia of maxillae with 15–16 comb-shaped bristles (Figs 20–22). Hypopharynx of lingua with tuft of small robust setae on anterior margin, superlinguae expanded laterally, densely covered with long and thin setae replaced before the apex by very small setae down to the lower part of the superlinguae (Fig. 15). Labium well developed, glossae dorsally with two distinct long setae (Fig. 23); glossae inner margin concave, outer margin serrated, and dorsal surface with numerous long hair-like setae (Fig. 24). Thorax. Pronotum moderately enlarged laterally, deeply concave medially, wider than the head, and basally not fused to the mesonotum (Figs 1, 4, 25), anterior margin of pronotum with a small projection at apex.Anteromedially with black or brown marking and posterior margin medially with black line (Figs 4, 25). Mesonotum with a mix of pale and brown color, anterolaterally with deep concavity (Fig. 25), and black posteriorly at lateroparapsidal suture. Legs yellowish brown with black markings (Figs 31–37). Foreleg: femur with marginal row of long strong bristles, anterior and dorsal surface with numerous blunt stout setae, medially with small black maculae and distally with a small black spot (Figs 31–33). Tibia inner margin with few sharp stout setae (Fig. 38). Tarsi without any setation. Midleg: femur dorsal surface with numerous long stout setae along with dorsal margin, medially with small black maculae, and distally with small black maculae (Figs 34–35); tibia outer margin with rows of numerous hair-like setae and dorsal surface with U-shaped patella-tibial suture (Fig. 39). Hindleg: similar to fore and midleg but the dorsal surface with arrow-shaped, blunt and strong setae (Figs 36–37). Tibia with dorsally 15–16 pointed bristles on marginal or submarginal position and U-shaped patella-tibial suture and tarsi outer margin with few hair-like setae (Figs 40–41). Claws of all legs with 3 blunt denticles (Figs 42–43). Abdomen. Posterolateral expansions on terga II–VIII and directed parallel to abdomen, slightly developed on terga II–III and well developed on terga IV–VIII (Figs 4–7). Dorsal surface of terga I–II pale with brown; tergum III with black with white spot; terga IV–VI with distinct four pale spots (Fig. 4); terga VII–VIII medially pale band and laterally brown; tergum IX with anteriorly pale and posterior brown band; tergum X 1/3 brown and pale bands (Figs 1–2); middle instar and mature larvae in slightly variable coloration (Fig. 4). Dorsal surface of sternum commonly pale, medially brown, and laterally light brown spots (Fig. 2); abdominal sterna III–VII with laterally pale brown streaks; sterna VII–IX medially very dark brown maculae (Figs 6–7). Sternum I, joining to the metanotum, has brown streaked maculae (Figs 9–10). Posterior margins of each tergum with irregular pointed teeth and a row of two microdenticles (Figs 28–29) and each tergum laterally with small simple setae. Gill I convex, asymmetrical, elongated, apically blunt, 2.5× longer than wide; ventral lamella, long fimbriate (Figs 44, 113); Gill II–VI strongly asymmetrical, length longer than width or subequal, tracheae well developed (Figs 45–49). Gill VII broad and apically blunt (Fig. 50). Cerci dark brownish with band pale increasing in size towards the apex. Paracercus dark brownish with yellow, with a dark brown band every 5–6 segments and each segment surrounded with pointed small yellowish spine-like bristles (Fig. 30). Genitals. Protopenis: male genitalia yellowish, apically blunt, and laterally expanded, segment X triangular and apically with numerous small setae (Fig. 27). Forceps proximally broad and distally narrow, simple. Adult. Unknown. Etymology. The species name “ bengalensis ” refers to the state of West Bengal, India, from where the holotype and paratype specimens were collected. Distribution. Purulia district, West Bengal (India) (Fig. 111). Diagnosis. Thalerosphyrus bengalensis Vasanth, Kubendran & Subramanian sp. nov. is similar to T. meghalayensis but can be distinguished from all known species of Thalerosphyrus by the following combination of characters: (i) posterolateral expansions on terga II–III slightly developed and terga VI–VIII well-developed (Figs 2, 6–7); (ii) tergum III bears a broad black with white spot (Figs 1, 4–5); (iii) terga VII–VIII medially with a pale white band and laterally brown; tergum IX with anteriorly pale and posteriorly brown band (Figs 4–5); (iv) abdominal sterna III–VII with laterally brown streaks; sterna VII–IX medially very dark brown maculae (Figs 2, 6–7); (v) posterior margins of abdominal terga with irregular pointed teeth and a row of few micro denticles (Figs 28–29); (vi) pronotum moderately enlarged laterally, with ornamentation of anteromedian black marking (Fig. 25); (vii) all femora with various stout setae, medially black maculae (Figs 31–37); (viii) hind femur dorsal surface with triangle-shaped blunt setae tibia 15–16 pointed bristles on marginal or submarginal position (Fig. 40); (xi) claw with 3 blunt denticles (Figs 42–43); (x) gill I convex, asymmetrical, elongated, apically blunt, 2.5× longer than wide (Fig. 44); (xi) labrum expanded laterally, 4.5× wider than long, anterior margin straight, medially bulged with a concave shape and small blunt crenations on either side, medio-ventrally with a curved row composed of 10–11 long stout setae (Figs 12–14); (xii) hypopharynx broad, lingua apically with small setae and superlinguae expanded laterally (Fig. 15); (xiii) maxillae broad, galea-lacinia with 15–16 comb-shaped bristles (Fig. 20); (xvi) glossae broad, inner margin concave and outer margin serrated (Fig. 24).