Austrolimnius (Telmatelmis) hintoni Arce-Pérez & Reynoso, 2025

Austrolimnius (Telmatelmis) hintoni Arce-Pérez & Reynoso NEW SPECIES

( Figs. 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Diagnosis. Males of Austrolimnius hintoni sp. nov. can be distinguished from other species in the genus by the following combination of features: metatibiae notched on mesal margin at 3/4, forming a concavity partially concealed by a patch of golden setae. Hind trochanter unarmed, pronotum with a longitudinal median sulcus almost as wide at base as at apex, and third interval of elytra with a short carina near base, reaching almost 1/10 the elytral length. Additionally, the male prosternal area behind base of prosternal process bare, without tuft of golden setae, and the genitalia with median lobe apically lanceolate and slightly longer than parameres, which are fused in basal third. Females must be identified by association with contemporaneously collected males.

Description. Holotype male. Length 1.73 mm; maximum width 1.00 mm. Paratypes (n = 10), length 1.73–1.85 mm (mean = 1.79 mm); maximum width 0.90–1.20 mm (mean = 1.12 mm). General shape suboval; widest across metasternum, in front of metacoxae; overall dorsal coloration dark-brown to dark-reddish-brown; antennae light-brown to yellowish; legs brown to reddish-brown, yellowish apically; short and whitish scattered setae on pronotum, forming faint longitudinal lines on elytra ( Fig. 1A View FIGURE 1 ). Overall ventral coloration dark-reddish-brown, primarily dark-brown on head and along thorax midline; mouthparts yellowish. Whitish to silvery plastron ventrolaterally on head, prothorax, mesothorax, metathorax, and abdominal segments 1–5 ( Fig. 1B View FIGURE 1 ).

Head. Subtriangular, tapering toward labrum; length 0.17 mm; maximum width behind eyes 0.18 mm; gena with plastron setae; vertex with inverted V-shaped sulcus, extending from posterior margin of eyes toward occiput ( Fig. 1 View FIGURE 1 inset). Eyes large, not protuberant. Antennae filiform, light-brown to yellowish, mostly glabrous, shorter than pronotum, antennomeres 1–10 cone-shaped, antennomere 11 ovoid. Maxillary palpus four-segmented, fourth palpomere slightly longer, tapering apically. Labial palpus three-segmented, third palpomere flattened.

Thorax. Pronotum: subquadrate, convex, slightly wider than long; length 0.57 mm; width 0.70 mm, widest at basal third. Anterior and lateral margins convex; posterior margin sinuate, medially embracing convex anterior margin of scutellum. Medial longitudinal sulcus narrower in the middle; posterior width 0.10 mm; medial width 0.05 mm; anterior width 0.07 mm. Laterally with a longitudinal sublateral carina extending from posterior margin to almost anterior margin. Scutellum: small, triangular, slightly protuberant. Elytra: wider than pronotum, completely covering the abdomen, broadly rounded apically ( Fig. 1A View FIGURE 1 ); length 1.15 mm; maximum width 1.00 mm. Each elytron with six conspicuous longitudinal rows of round punctures, third interval with a short carina reaching almost 1/10 the elytral length, and two well-developed sublateral carinae extending from base to almost posterior margin ( Figs. 1A, 1B View FIGURE 1 ). Two of the rows of punctures placed between sublateral carinae; punctures smaller than the rest. Epipleuron with plastron setae and two longitudinal rows of round granules extending from base to almost posterior margin. Prosternum: long, tongue-shaped, without evident impressions. Basal half subrectangular, anterior margin slightly concave, lateral margins almost straight. Prosternal process with lateral margins tapering to a broadly rounded apex, surpassing anterior margin of mesocoxae. Prosternal episternum, epimeron, and hypomeron with plastron setae ( Fig. 1B View FIGURE 1 ). Mesoventrite: short, wide; anterior margin with deep concavity concealed by prosternal process. Mesosternal episternum and epimeron with plastron setae. Metaventrite: almost twice as wide as long at midline; anterior margin concave to receive prosternal process; disk smooth, flanked by an arched carina, with a medial longitudinal depression. Metasternal episternum with plastron setae ( Fig. 1B View FIGURE 1 ). Legs: brown to reddish-brown, tarsi yellowish. Pro- and mesocoxae rounded, metacoxae transversal. Trochanters subtriangular, without impressions. Femora robust, oblong, with scattered granules and recumbent white setae, covered with plastron setae. Tibiae with minute and small denticles on distal half of external and internal margins, respectively, with a longitudinal fringe of long, yellowish-golden setae laterointernally on distal half of dorsal margin. Pro- and mesotibiae subequal, slightly wider in distal half. Metatibiae longest, with subapical, shallow, oval concavity on distal fourth of dorsal margin ( Fig. 1A View FIGURE 1 , encircled detail); distal half of concavity with a comb row of 7–10 stout, spine-like setae along lateroexternal margin ( Fig. 1C View FIGURE 1 , encircled detail); fringe of long setae widening apically to cover basal half of concavity ( Fig. 1A View FIGURE 1 , encircled detail). Tarsus yellowish; tarsomeres 1–4 with fine setae ventrally, tarsomere 5 with scant, fine setae ventrally; length of tarsomere 5 subequal to combined lengths of tarsomeres 1–4. Tarsal claws slender, acute.

Abdomen. With five ventrites; ventrites 1–4 with plastron laterally, broader coverage toward posterior ventrites; ventrites glabrous medially (possibly abraded); ventrites 1 and 5 longest at midline, ventrites 2–4 of similar length medially; ventrite 1 between metacoxae semicircular; ventrite 5 longest, subtriangular, apex broadly rounded ( Fig. 1B View FIGURE 1 ), with a faint oval impression medially on posterior third. Genitalia: length 0.86 mm; phallobase long, length 0.55 mm, about twice the length of parameres. Parameres in dorsal view slightly shorter than median lobe, length 0.28 mm, fused in basal third, area between parameres dagger-shaped, tuft of long setae arising posterolaterally ( Fig. 2A View FIGURE 2 ); lateral margins almost straight in basal two thirds, apical third slightly concave basally, convex apically; distance between lateral margins widest across apical convexities ( Fig. 2A View FIGURE 2 ). In lateral view ( Fig. 2B View FIGURE 2 ), parameres with a constriction at base of apical third, more prominent on ventral margin; apex subtriangular, not at same level as apex of median lobe. In ventral view ( Fig. 2C View FIGURE 2 ), parameres with basal two thirds subrectangular, almost twice as wide as apical third; inner margins sinuate in basal two thirds, curved laterally, then medially and laterally anew to form a subrectangular notch and a finger-like process at base of apical third, respectively; distal part concave. Median lobe in ventral view slightly longer than parameres, length 0.31mm; in dorsal view distal 1/8 visible, pointed apically ( Fig. 2A View FIGURE 2 ); in lateral view, distal third slightly deflexed ventrally, below level of apex of parameres ( Fig. 2B View FIGURE 2 ); in ventral view, slightly narrowed at apex of median third, distal third lanceolate ( Fig. 2C View FIGURE 2 ).

Allotype female. Paratypes (n = 10), length 1.65–1.75 mm (mean = 1.70 mm); maximum width 0.90–1.00 mm (mean = 0.95 mm). Coloration and proportions same as for holotype. Otherwise all tibiae slightly wider apically, with fringes of setae on distal half of internal margin; hind tibiae without subapical concavity on distal fourth of dorsal margin. Genitalia: ovipositor lightly sclerotized, hyaline, length 0.70 mm; valvifer with two sclerotized rods, length 0.40 mm; gonocoxites length 0.27 mm, together cloven hoof-shaped in basal half, distal half pandurate, about 0.5× the width of basal half, surface with scattered micropunctures; styli oblong, length 0.04 mm ( Fig. 3 View FIGURE 3 ).

Variation. Generally, males and females are similar, with a length of 1.70–1.85 and maximum width of 0.9–1.2. In both sexes, the rows of punctures between sublateral carinae can be truncated or merged into a single row in posterior half. Also, in both sexes the length of the small denticles on all tibiae can be variable (possibly due to abrasion).

Comparative notes. Austrolimnius (Telmatelmis) hintoni sp. nov. can be easily distinguished from other North American (including the Central American subregion) congeners by the presence of an oval concavity on the dorsal margin of the male metatibiae. Also, it can be distinguished from A. eris because this species belongs to the subgenus Helonoma and lacks the medial longitudinal sulcus on the pronotum. Dissimilar features on remaining North American species also in the subgenus Telmatelmis include (features of A. hintoni are those in parentheses): A. formosus has a fusiform body shape and lacks the carina at base of third elytral interval (suboval body shape and short carina present); A. curtulus has the median sulcus of the pronotum almost twice as wide at apex as at base (almost same width at apex and base) and a long carina in third elytral interval (short carina); males of A. halffteri possess a tuff of golden setae on the prosternum, behind the base of the prosternal process, and a tuff on the side of the metasternal disk, behind the middle coxa (without such tuffs on ventral surface); males of A. sulcicollis present a row of teeth on the posterior margin of hind trochanters and an apical denticle on the internal margin of hind tibiae (without such teeth and denticle).

Additionally, based on available literature, the new species can be distinguished from some South American consubgeners by the following characteristics (features of A. hintoni are those in brackets): males of A. tarsalis Hinton , A. egregius Delève , and A. browni Hinton have two prosternal teeth between the sublateral carinae, in front of the procoxal cavities ( Hinton 1971) [males without such prosternal teeth]; A. mucubajiensis Gómez & Bello has a body length of 4.48 mm and the pronotal medial sulcus narrow posteriorly and widening anteriorly ( Gómez & Bello 2006) [body length <2 mm and medial sulcus wider posteriorly]; A. cleidecostae Polizei , Costa & Bispo has a body length of 1.18–1.20 mm ( Polizei et al. 2020) [body length of 1.65–1.85 mm]; A. browni Hinton with parameres and median lobe longer than phallobase ( Hinton 1971) [parameres and median lobe shorter than phallobase].

Habitat description. The type locality at Río Huehueyapan (Sección La Marina) is in the central part of eastern Mexican state of Veracruz at 1,200 m.a.s.l. At this locality the river is shallow and the substratum is mainly composed of gravel and cobble ( Fig. 4 View FIGURE 4 , photographs from September 2024).

Distribution. This new species is hitherto known to be present only in the eastern Mexican state of Veracruz, in streams at 1200–1800 m.a.s.l. The three localities are in the central part of the state ( Fig. 5 View FIGURE 5 ), on the border between the eastern section of the Trans-Mexican Volcanic Belt and the Veracruzan biogeographic provinces. This species was collected syntopically with A. sulcicollis at the type locality and at arroyo Ahuacatlán.

Etymology. The specific epithet hintoni is in honor of Professor Howard E. Hinton (San Luis Potosí, Mexico, 24 August 1912 – Bristol, England, 2 August 1977), a distinguished entomologist and Head of the Department of Zoology at the University of Bristol, in recognition of his outstanding contribution to the knowledge of the species in the genus Austrolimnius around the world.

Repositories. The holotype, allotype, and most paratypes will be deposited in the IEXA ; additional paratypes (2♂, 2♀ each) will be deposited in the CNIN, EMEC , and USNM.

Type material examined. HOLOTYPE ♂. MEXICO: VERACRUZ: Mpio. Coatepec, Coatepec, Río Huehueyapan ( Sección La Marina ), 19º26'55''N, 96º58'52''W, 1200 m, Bosque Mesófilo de Montaña , 28-VII-1994, Arce-Pérez , R. col GoogleMaps . ALLOTYPE ♀: same data as holotype GoogleMaps . PARATYPES: same data as holotype but 21-IV-1994 (1♂, 1♀ IEXA) GoogleMaps ; same but 28-VII.1994 (2♂, 2♀ CNIN; 2♂, 2♀ EMEC; 2♂, 7♀ IEXA; 2♂, 2♀ USNM) ; same but 02-IV-1997 (1♂, 4♀ IEXA) ; same but 18-V-2000 (1♂, 4♀ IEXA) ; same but 22-III-2001 (3♂, 8♀ IEXA) ; same but 24-III-2001 (1♂, 1♀ IEXA) ; same but 26-IV-2001 (12♂, 8♀ IEXA) ; same but 30-IV-2001 (3♂, 8♀ IEXA) ; same but 07-VII-2001 (1♂, 3♀ IEXA) ; same but 06-VIII-2001 (1♀ IEXA) ; same but 17-III-2002 (2♀ IEXA) ; same but 01-V-2002 (1♂, 2♀ IEXA) ; same but 28-VIII-2002 (2♂, 1♀ IEXA) ; Mpio. Coatepec , Arroyo Ahuacatlán, cascada Los Tecajetes, 19º28'19.90''N, 96º59'04.65''W, 1369 m, 29-III-2001, Arce-Pérez, R. col. (8♀ IEXA) GoogleMaps ; same but 15- IV-2001 (8♀ IEXA) ; Mpio. Xico , Xico Viejo, Río Malseseca, 19º26'44.89''N, 97º03'22.22''W, 1800 m, 30-VIII-1997, Arce-Pérez, R. col. (6♂, 7♀ IEXA) GoogleMaps .