Choroterpes ( Dilatognathus ) triapicalis Vasanth, Kubendran & Subramanian, 2025

Choroterpes ( Dilatognathus) triapicalis Vasanth, Kubendran & Subramanian sp. nov.

( Figs. 3, 6 View Figs , 9, 12 View Figs , 69-94 View Figs View Figs )

Material examined: Holotype: 1 mature larva, INDIA, Himachal Pradesh, Solan, Giripul Ganga River , 30.5333° N, 77.1236° E, 1600 m, 09.vi.2018, Coll. T. Kubendran GoogleMaps . Paratype: 14 larvae, same data as holotype GoogleMaps . 5 larvae, Jammu and Kashmir, Udhampur, Tawi River, Chenani ,

33.03122° N, 75.20751° E, 1011 m, 14.xi.2018, Coll. T. Kubendran and Akil Nair. 11 larvae, INDIA, Himachal Pradesh, Mandi, Janjehli, Bakhli River , 31.51171° N,

77.21943° E, 2101 m, 11.xi.2019, Coll. T. Kubendran .

Description: Mature larva ( Fig. 3 View Figs ): Body yellowish brown; length 7-8 mm; caudal filament 5-6 mm; antennae 2.3-2.5 mm ( Fig. 94 View Figs ).

Head: Head prognathous, yellowish with black markings; three distinct black ocelli with white colour markings. The upper layer of the head is shallow. Eyes with yellowish and lateral black ( Fig. 9 View Figs ). Labrum wide, (4.2:1.6=width and length of middle) shallow emargination anteriorly, with a row of long 11-12 hair-like setae on the dorsal surface and small simple hair-like setae, lateral margin wide with long dense hair-like setae ( Fig. 69 View Figs ); ventral surface with small hair-like setae. Hypopharynx well-developed lateral process, lingua wide with laterally curved, superlingua rounded anterior and hands wide laterally ( Fig. 70 View Figs ). Mandibles curved smooth laterally with dense hair-like setae. Left mandible: incisors fused; inner and outer incisors with 3+2 teeth; inner incisor wide compared to outer; inner incisor almost same as outer incisor; prostheca narrow with hair-like setae; margin between prostheca and mola convex; dorsal margin without setae under mola; mola with above 6 chambers and small setae ( Figs. 71-73 View Figs ). Right mandible: incisors fused; outer and inner incisors with 3+2 teeth; inner incisor slightly smaller than outer incisor; prostheca long and hair-like setae; margin between prostheca and mola concave and gradually increase the mola convex; dorsal margin with 5-6 long setae under mola; outer margin with convex triangular and closely large chamber with medially stout setae ( Fig. 74 View Figs ). Maxilla long with palp III segmented; maxilla with inner-apical angle produced as long as a tusk-like process; palp elongated and bears long filtering simple setae; galea-lacinia outer margin convex with long and small simple hair-like setae; inner margin with dense hair-like setae; crown inner and outer long hair-like setae; segment I inner margin convex and outer margin with 5-6 simple setae; segment II inner side concave with 5 long, simple setae, outer side with 2-3 small setae; segment III apically blunt with dorsal proximally transverse row of long setae, on inner side with a row of numerous long, simple setae, outer side with apically long simple setae ( Fig. 75 View Figs ). Labium; glossae laterally rounded, anterior margin covered with small stout setae; paraglossae wide, laterally expanded with the blunt spine, dorsal surface with medium dense hair-like setae, small stout setae and anterior margin with rows of dense long hair-like setae; palps elongated, III segmented, with long and wide filtering and longitudinal setae; segment I wide, outer margin with a row of numerous simple setae; segment II outer margin with rows of long, simple hair-like setae and dorsal surface with rows of numerous long, simple hair-like setae, ventral surface with three rows of long setae ( Figs. 76-78 View Figs ).

Thorax: Notum dorsally yellowish with diffuse black marking on lateral ( Fig. 3 View Figs ); small spine-like humeral setae on prothorax ( Fig. 94 View Figs ), ventral surface with pale white without any markings ( Fig. 6 View Figs ). Legs yellowish black; each femur with black markings on basal, middle and apex; basal of the mid and hind tibia with black colour marking and fore tibia with black marking on base and apex. Foreleg: proximal and middle of femur wide, distally narrow; dorsal surface with proximal long, simple apically rounded setae; mid and distal with black marking and numerous simple apically rounded setae, proximal with diffuse black marking and anterior margin with long simple setae, simple apically rounded setae; posterior margin with small simple setae and small feathered setae; inner margin of the tibia with a row of long, feathered, simple setae, dorsal surface with a row of irregular small setae; outer margin with long hair-like setae; inner margin of tarsi with a row of simple setae, dorsal surface with small simple setae, outer surface with hair-like setae ( Figs. 79- 82 View Figs ); claw apically sharp with 10-11 denticles, separate into 2 parts, basally 3 denticles and apically 7-8 denticles ( Fig. 82 View Figs ). Middle leg ( Figs. 83-85 View Figs ): dorsal surface of femora with small spine-like setae on proximal and long simple apically rounded setae near apex; anterior margin with long hair-like setae and irregular apically rounded setae in various lengths; posterior margin with irregularly long apically rounded and small stout setae; inner margin of the tibia with irregularly spine-like setae, outer margin with long hair-like setae, dorsal surface with small stout setae; tarsi outer and inner margin with hair-like and dorsally small stout setae. Hind leg ( Fig. 86 View Figs ): dorsal surface of the femur with apically rounded setae of various lengths, small stout setae, anterior margin with long dense apically rounded setae and hair-like setae, posterior margin with numerous apically rounded setae; tibiae inner and outer margin with rows of apically rounded setae, hair-like and feathered setae, dorsal surface proximally with apically rounded setae and mixed with hair-like setae; tarsi inner and outer margin hair-like setae and dorsal surface small stout setae, claw apically blunt with 11-12 denticles, separate into 2 parts, basally 4 denticles and apically 7-8 denticles. Hind wing pad present.

Abdomen: Dorsal surface of terga I-VI brownish, tergum VII yellowish and terga VIII-X brownish yellow, terga IV-V with small band medially ( Fig. 3 View Figs ); posterolateral margins of abdominal terga I-VI without denticles and terga VII-IX pointed denticles ( Figs. 3 View Figs , 87 View Figs ). Posterior margin of abdominal terga I-X with a row of triangular denticles ( Fig. 87 View Figs ); terga VIII-IX with irregular row of spines medially; sterna pale white, absence of denticles on posterior margin, sternum IX with brown line marking medially on posterior margin ( Fig. 6 View Figs ). Gills present on terga II-VII, black colour; each gill has two lamellae, gill II-VII with 6 apical processes ( Figs. 88-93 View Figs ), gill VII present with 6 apical processes ( Fig.93 View Figs ), dorsal and ventral lamella with three processes; dorsal lamella medially with small apical processes. Caudal filament, black colour with a whorl of setae on alternate segments; setae smaller than the length of the corresponding segment.

Adult: Unknown

Etymology: The species is named “ Choroterpes ( D.) triapicalis ” with “triapicalis ” indicating the presence of six apical processes on the seventh gill, where “tri” denotes “three” and “apicalis” refers to “apical” processes. This naming convention reflects a specific morphological characteristic of the species, providing valuable information for its taxonomic identification and classification.

Distribution: Himachal Pradesh & Jammu Kashmir (UT) India.

Diagnosis: Choroterpes ( D.) triapicalis sp. nov. is similar to Ch. ( D.) latus sp. nov. it can be differentiated from all other known species of the subgenus by the following combination of characters: (i) labrum wide, shallow emargination with long 11-12 hair-like setae on the dorsal surface ( Fig. 69 View Figs ); (ii) lingua wide and curved laterally ( Fig. 70 View Figs ); (iii) inner incisor of left mandible wide with 2 teeth, basally wide, mola with 6 chambers ( Figs. 71-73 View Figs ); (iv) segment III of labial palp long and wide; paraglossae laterally with the blunt spine ( Figs. 76-78 View Figs ); (v) middle and distal of all femur with distributed black colour ( Figs. 79, 83, 86 View Figs ); (vi) claw apically blunt with 11-12 denticles, separate into 2 parts, basally 4 denticles and apically 7-8 denticles ( Fig. 85 View Figs ); (vii) gill VII present, six apical processes; dorsal and ventral lamella with three processes; dorsal lamella medially with small apical processes ( Fig. 93 View Figs ).

Biological notes: The type-locality is in a remote area of 23 km from the district of Solan, Himachal Pradesh ( Fig. 96 View Figure 96 ). The Giripul Ganga River bed is mostly composed of gravel, sand and silt. The Giri Ganga River with 4-4.8 m wide and 35 cm depth and has medium water current ( 1.2 m /sec.) on the eastern part of Western Himalaya. The water temperature ranged between 17-20°C (seasonal variations) and the pH between 6.5 and 7.0. The larvae were collected at the stony bottom found edge of the Giripul Ganga River.