Arisemus nahuiollin Durán-Luz & Ibáñez-Bernal, 2025

Arisemus nahuiollin Durán-Luz & Ibáñez-Bernal sp. nov.

( Figs. 1–15 View FIGURES 1−5 View FIGURES 6−9 View FIGURES 10−15 )

Diagnosis. Arisemus nahuiollin sp. nov. is distinguished from other Arisemus species by the following combination of characters: antennae with scape long, 3.6 times the length of the spherical pedicel; palpus reaching flagellomere 10; wing infuscate with dark spots on vein apices. Male with scent organ on the anepisternum that has the shape of a flower with four petals. Male terminalia with narrow laminar, truncate anteriorly, anterior gonocoxal condyles; aedeagus thin; parameres slightly curved outwards near base, with the apical portion parallel sided and sharp apex, and supporting a membranous parameral sheath. Female genitalia with the external margin of hypovalvae nearly straight.

Male description ( Figs. 1–9 View FIGURES 1−5 View FIGURES 6−9 ). Head piriform in frontal view, vertex triangular with surface covered with setae alveoli, except by a longitudinal line at middle. Eyes contiguous, eye-bridge with three rows of facets. Frontal patch of alveoli divided at midline, with lower margin almost straight, and upper margin bilobed. Palpus long, reaching flagellomere 10, proportion of palpal segments: 1.00: 0.89: 1.22: 1.78 ( Fig. 1 View FIGURES 1−5 ). Antennae with scape long, 3.6 times the length of the spherical pedicel; flagellum with 14 flagellomeres, flagellomere 1 partially fused to flagellomere 2, flagellomere 1–11 nodiform, flagellomeres 12–14 smaller, 12–13 oval, 14 pyriform; flagellomere 3 with only one ascoid which is smaller than those of flagellomeres 4–11, flagellomeres 4–11 with pairs of simple short digitate ascoids ( Figs. 1–3 View FIGURES 1−5 ). Labium with inverted Y-shaped sclerite and 3 small spiniform setae at each side of “Y” sclerite stem; labella with 5 tooth-like sensilla on the internal margin ( Fig. 4 View FIGURES 1−5 ).

Wing 3.1 times longer than width, slightly infuscate, with dark spots on all vein apices and base of R 5, and with white spots between vein apices; radial sector pectinate; radial and medial forks complete, CuA 2 not reaching wing margin, its apex exceeds the level of medial fork ( Fig. 5 View FIGURES 1−5 ). Anepisternum with a scent organ as a flower with four petals, its diameter as the anterior spiracle ( Figs. 6, 7 View FIGURES 6−9 ).

Aedeagus slightly asymmetrical, long, with the apex acute, ejaculatory apodeme expanded anteriorly, as long as aedeagus and with a large hole. Parameres triangular in dorsal view, reaching the distal portion of gonocoxite, connected by a strongly sclerotized U-shaped band, and supporting a dorsal membranous parameral sheath. Gonocoxite simple with a patch of short setae, on a strongly sclerotized inner apical region; anterior condyles of gonocoxite large, in dorsal view, wider in the middle, tapering towards the anterior portion with margin truncated. Gonostylus is simple, slightly shorter than gonocoxite, tapering towards the apex, apex sinuous ( Fig. 8 View FIGURES 6−9 ). Epandrium almost square, epiproct triangular homogeneously pilose, wider than long, with apex round; hypoproct longer than wide, with setae on the distal region. Hypopod as long as epandrium, tapering towards apex, with one spatulate tenaculum at apex; hypandrium as a thin band ( Fig. 8 View FIGURES 6−9 ).

Measurements. (n=4). Head width: 0.375 (0.36–0.40); head length: 0.403 (0.38–0.43); length from vertex to the dorsal margin of eye: 0.173 (0.16–0.18); labrum length: 0.105 (0.10–0.11); proboscis length: 0.115 (0.11–0.12); palpus length: 0.465 (0.43–0.50); antenna length: 0.768 (0.75–0.79); wing length: 1.608 (1.56–1.67); wing width: 0.520 (0.51–0.53); epandrium width: 0.180; epandrium maximal length: 0.160; hypopod length: 0.190 (0.18–0.21); gonocoxite length: 0.130; gonostylus length: 0.115 (0.11–0.12); aedeagus length: 0.308 (0.29–0.33).

Female description ( Figs. 10–15 View FIGURES 10−15 ). Like male, except by the following characteristics: palp reaching flagellomere 11, proportion of palpal segments: 1.00: 1.13: 1.13: 2.13 ( Fig. 10 View FIGURES 10−15 ). Antenna with scape 1.7 times the length of pedicel; flagellomere 3 with one ascoid, and flagellomeres 4–11 with a pair of digitiform ascoids ( Figs. 11, 12 View FIGURES 10−15 ). Wing like male, as long as 3.1 times its width ( Fig. 13 View FIGURES 10−15 ).

Genital plate homogeneously pilose, longer than wide, calyx-like, with a long neck, and apically bilobed (hypovalvae); hypovalvae external margin nearly straight, both separated by a slight concavity ( Figs. 14, 15 View FIGURES 10−15 ). Ventral receptacle with a pair of semispherical structures anteriorly, which are supported by wide strongly sclerotized outwards curved rods. Genital chamber with a central hole and two groups of three spiniform setae near it, with an elongated membranous plate ( Fig. 14 View FIGURES 10−15 ). Cerci 1.2 times larger than genital plate, tapering toward apex ( Fig. 15 View FIGURES 10−15 ).

Measurements. (n=7). Head width: 0.360 (0.32–0.39); head length: 0.401 (0.36–0.42); length from vertex to the dorsal margin of eye: 0.167 (0.14–0.18); labrum length: 0.099 (0.09–0.11); proboscis length: 0.109 (0.10–0.12); palpus length: 0.436 (0.40–0.47); antenna length: 0.725 (0.70–0.74) n=4; wing length: 1.767 (1.55–1.92); wing width: 0.581 (0.50–0.61); width of genital plate: 0.200 (0.18–0.21); total length of genital plate: 0.224 (0.21–0.24); cerci length: 0.294 (0.28–0.30).

Material examined. Holotype ♂: Mexico, Puebla, Jolalpan, Rancho El Salado (18° 20'40.7"N, 98° 57'15.9"W, altitude 948 m), CDC light trap, J. Durán-Luz, col. 02-v-2015, 1 ♂ GoogleMaps . Paratypes 3 ♂, 7 ♀: same data as holotype, except: 03-v-2015, 1 ♀ GoogleMaps ; Malaise trap (18° 20'20.6"N, 98° 57'15.7"W, altitude 937 m), 12–14-ii-2017 1 ♂, 4 ♀. GoogleMaps

Etymology. From the Nahuatl language and Aztec symbol nahuiollin ; nahui, four, ollin, movement. From the symbolic point of view, the four primordial forces of the universe water, earth, fire and air were represented by four petals, being the five sun the center, which is the one we live with. It is represented by a four-petal flower in various sculptures and ancient engravings. We name this species referring to the shape of the male scent organ.

Type locality. Mexico, Puebla, Jolalpan, Rancho El Salado.

Comments. Arisemus nahuiollin most resembles Arisemus imeldae Ibáñez-Bernal & Suárez-Landa, 2017 , but the male of A. imeldae has a large morular scent organ on anepisternum, rounded gonocoxal condyles, thicker parameres, and the aedeagus wider not tapering towards apex, whereas the female of A. imeldae has hypovalvae with the external margin rounded and lacks the three small setae at each side of the central hole of the genital chamber.