Dixella machiotla Huerta & Ibáñez-Bernal 2023, sp. nov.
Creators: name: Huerta, Herón
name: Ibáñez-Bernal, Sergio
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Dixidae
Dixella
Dixella machiotla

description: Dixella machiotla sp. nov.
(Figs. 1, 3–7)
Type specimens. HOLOTYPE male (mounted on microscope slide). MEXICO, Hidalgo, Tlanchinol, km3.5 carretera Tlanchinol–Apantlazol, GPS: 20º 59’ 16” N, 98º 39’ 36” W, 8˗apr˗1997, Malaise trap, leg. Salceda-Sánchez, B., Pérez– Garcia,A. & Blackaller-Bages, J. (CAIM). PARATYPES: Same data as holotype, except, 7˗apr˗1997, 2 males, 5 females (preserved in 75% ethanol); 8˗apr˗1997, 5 males, 3 females (preserved in 75% ethanol); 9˗apr˗1997, 2 males (slide); 23˗nov˗1997, light trap, leg. Ibáñez ˗ Bernal, S., 1 male (pin), 3 males, 3 females (IEXA), and 7 males, 5 females (CAIM).
Diagnosis. Clypeus pale, with traverse basal dark band; katepisternum dark brown, with a small pale spot at middle on the posterior margin; wing with faint dark spot over crossvein r-m; R 2+3 originating from R; male genitalia with tergum 10 U–shaped, with a pair of setose subapical lobes; gonostylus talon-like, but with a rounded ventrolateral flange with a distintive digitiform process mesially directed. Female: tergum 9 with a pair of well˗development posterolateral lobes.
Description. Male. Head (Fig. 3A) dark brown, ovoid, twice as wide than long in frontal view; separation between eyes 0.37 mm (n=2); antenna dark brown, flagellum length 1.52 mm; all flagellomeres cylindrical, the first flagellomere length /wide proportion= 10.4, and 2X longer than second flagellomere (Fig. 3B). Clypeus pale, slightly wider than long, with traverse basal dark band; Maxillary palpus five-segmented, brown, length 0.4 mm.
Thorax (Fig. 3C, D). Scutum with wide brown medial vitta extending from anterior margin to middle of scutum, tapering to posterior margin, anteriorly continuing to dark brown lateral vitta; with rows of acrostical, dorsocentral and lateral prealar fine setae. Scutellum pale brown; mediotergite dark brown. Pleura dark brown with pale areas. Postpronotum pale, with small diffuse anterior brown spot. Anterior anepisternum pale, with brown spot. Posterior anepisternum dark brown. Katepisternum dark brown, with small pale spot at middle of posterior margin. Anepimeron dark brown, except by anterior margin with an irregular pale area.
Wing. (Fig. 4A). Length (n=3), 2.8 mm, width (n=3), 1.02 mm. Membrane pale with light dark spot over crossvein r-m. Wing veins brown, setose, except crossvein r-m and crossvein m-m; Sc elongate, extending more than 0.39 length of wing, ending in C, slightly before at level of the Rs origin. R 2+3, arched, originating from R; stem of R 2+3 0.32 length of R 3. Crossvein m-m discontinuous towards crossvein r-m. Halter brown, 0.38 length of fore femur.
Legs. Coxae and trochanters pale, except the base of fore coxa which is dark brown; femora and tibiae yellowish with dark brown apices, more distinctive on hind tibia; hind tibia with narrow longitudinal ridge proximal to comb near dorsal margin; claws of all legs with 3 anterior setae and 1 basal seta (Fig. 3E).
Terminalia (Fig. 5A–D, 6A–C). Tergum 9 setose, posterior margin slightly produced, anterior margin slightly emarginated. Sternum 9 with posterior margin slightly produced. Gonocoxite stout, as long as basal width, tapering to apex; gonocoxal apodeme and basal lobe not development; apical lobe 1.2X longer than gonostylus, base slightly curved, stem stout, tapering to apex, with pointed tip laterally curved. Gonostylus talon-like, but with a rounded ventrolateral flange. Paramere filiform, slightly curved base, stem directed anteriorly, apices with recurved rounded tip. Aedeagus thin, triangular, connected to the base of the paramere and anteriorly directed. Tergum 10 U–shaped, sclerotizated, basolateral process recurved anteroventrally, stem sinuose, a pair of setose, subapical lobes; posterior margin slightly emarginated.
Female. As in male, but with following differences: Head width 0.6 mm. Flagellum length 1.55 mm. Wing (Fig. 4B) length 3.15 mm, width 1.17 mm. Terminalia (Fig. 7A, B): tergum 8 brown with pair of well˗developed posterolateral lobes; sternum 9 narrow, forming a band medially directed; tergum 9 dark brown, with short, posterolateral lobes; segment 10 shorter than cerci, subtriangular; cercus dark brown, subcylindrical. Spermatheca spherical.
Distribution. This species is known only from the type locality, Tlanchinol, Hidalgo state, Mexico (Fig. 1, black square), at an altitude of about 1540 m.a.s.l., inhabiting a cloud forest.
Etymology. The specific epithet is from Nahualt language, abbreviation of the word “ icpimachiotl ”, meaning “cloud forest”.
Remarks. This new species is distinguished from other Neotropical species of Dixella principally by the dark brown katepisternum having a small pale spot at posteromedial margin and gonostylus subsquared, with a distinctive mesially directed digitiform process. Dixella machiotla has a scutal color pattern similar to the following Costa Rican species: Dixella maculata Chaverri & Borkent, 2007, D. lobata Chaverri & Borkent, 2007, D. hernandezi Chaverri & Borkent, 2007 and D. suzukii Chaverri & Borkent, 2007. Dixella maculata and D. machiotla share the presence of a posterolateral lobe on tergum 9; the Costa Rican species mentioned are distinguished by wing having a distinct large dark spot over crossvein r-m, while D. machiotla has but a faint spot there. Also, D. machiotla has tergum 10 U-shaped, basolateral process recurved anteroventraly, and gonostylus talon-like, with a rounded ventrolateral flange.
Dixella is widely known in the Neotropical Region, where it easily comprises the largest clade within the family (Lane 1942, 1953; Stone 1966; Belkin et al. 1970; Peters 1980; Chaverri & Borkent 2007). Several of these species require thorough redescription, especially fine details of the male genitalia. Chaverri & Borkent (2007) provided a comprehensive review of the Costa Rican species, resulting in a tally of 10 confirmed species, eight of which were described as new. Moulton (2016, 2017) using tandem morphological and molecular study provided the first evidence of cryptic species within the family, both instances within the comparatively well studied Nearctic fauna.
In Mexico, previous records of the genus Dixella are reported from the states of Baja California, Chiapas, Coahuila, Morelos, Nuevo León, Oaxaca and Veracruz (Peters & Cook 1966; Heinemann & Belkin 1977; Huerta & Ibáñez-Bernal 2021); many of these records, however, are based on undetermined species. The presence of this new species in Hidalgo state along with discovery of D. aliciae in Morelos state demonstrate the ubiquity of Dixidae in Mexico and help remediate the current state of Dixidae systematics there. Many species of Dixidae remain undiscovered around the world, even from areas considered well sampled (Wagner et al. 2008; Moulton 2016, 2017, 2018).
description: Published as part of Huerta, Herón & Ibáñez-Bernal, Sergio, 2023, Description of a new species of Dixella from a cloud forest in Tlanchinol, Hidalgo and first record of Dixella aliciae (Johannsen) in Mexico (Diptera: Dixidae), pp. 153-162 in Zootaxa 5353 (2) on pages 156-158, DOI: 10.11646/zootaxa.5353.2.5, http://zenodo.org/record/8427184