Dixella atitla Huerta & Ibáñez-Bernal, Huerta & Ibanez-Bernal, 2021

Huerta, Heron & Ibáñez-Bernal, Sergio, 2021, A new species of Dixella, the first Mexican record of Dixella shannoni, and a summary of dixid records from Mexico (Diptera: Dixidae), Zootaxa 5016 (3), pp. 430-440: 432-436

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Dixella atitla Huerta & Ibáñez-Bernal

sp. nov.

Dixella atitla Huerta & Ibáñez-Bernal   , sp. nov.

( Figs. 1–7 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 )

Type specimens. HOLOTYPE Male. MEXICO, Veracruz, Huatusco, Laguna de Santo Domingo, 22, February , 1992; leg. Ibáñez-Bernal, S. (mounted on microscope slide, in CAIM)   . Paratypes: Same data as holotype   , 1 ♂ ( IEXA)   , 1 ♀ ( CAIM)   , 1 ♀ ( IEXA)   .

Diagnosis. Dixella atitla   sp. nov. is unique among species of the Neotropical region with apical lobe of the gonocoxite hammer-like ( Figs. 5A, C–D View FIGURE 5 ) and gonostylus wider at base and dorsoventrally flattened, ending hookshaped, and at middle with a pair of short internal processes posteriorly directed ( Figs. 6A–E View FIGURE 6 ).

Description. Male. Head ( Fig. 1A View FIGURE 1 ) slightly wider than high in frontal view, dark brown; clypeus longer than width, pale yellow, with about 9 setae at disk. Antenna with scape, pedicel and flagellomeres dark brown, length 2.1 mm; all flagellomeres cylindrical, the first flagellomere length/ wide= 12.1, two times longer than second flagellomere; palpus brown, length 0.40 mm; palpomere ratios: 1.0: 3.0: 3.0: 3.5.

Thorax ( Figs. 2A, B View FIGURE 2 ). Scutum with wide dark brown medial vitta extending from anterior margin to middle of scutum, anteriorly narrowly continuing laterally to supra-alar area and lateral dark brown vitta. Scutellum (with six setae) and mediotergite dark brown. Pleura with pronotum, propleuron, anepisternum, katepisternum, anepimeron, and metanepisternum dark brown, except the distal part of anepimeron which is yellowish. Katepisternum bare.

Wing ( Fig. 3A View FIGURE 3 ). Length, 2.8 mm, width, 1.0 mm; membrane pale without dark spot over r-m; veins brown, setose except r-m and m-m; Sc elongate, extending more than 0.33 the length of the wing, ending in C, slightly before at level of the origin of the Rs; R 2+3, arched, originating distal to r-m; stem of R 2+3 0.25 length of R 3. Halter brown, 0.34 the length of fore femur.

Legs. Coxae and trochanters pale yellow, except the base of fore coxa which is dark brown; femora yellowish with brown apices; tibiae pale brown with brown apices, more distinctive in hind tibia; hind tibia with a narrow longitudinal ridge proximad of comb near dorsal margin, apparently consisting of fused spicules ( Fig. 2C View FIGURE 2 ); claws of all legs with external basal seta ( Fig. 2D View FIGURE 2 ).

Terminalia ( Figs. 4‒6 View FIGURE 4 View FIGURE 5 View FIGURE 6 ). Tergum 9 ( Fig. 4A View FIGURE 4 ) with anterior margin slightly emarginated, posterior margin pro- duced medially, with lateral setae. Sternum 9 ( Fig. 4B View FIGURE 4 ) with posterior margin slightly emarginated, with scattered setae. Gonocoxite slightly longer than wide; gonocoxal apodeme small and capitate; basal lobe not visible; apical lobe similar to the length of gonostylus, hammer-like, stem curved subapically with a long seta, apically with two opposite processes. Gonostylus dorsoventrally compressed, wider basally with scattered setae on ventral surface, with a pair of processes, one long than the other, the medial process with a setose rounded tubercle. Apodemes dark brown, slim and pointed (not completely visible in figures as in the slides they are ventrally oriented) ( Fig. 6A View FIGURE 6 ); parameres triangular at base, hook-shaped at apex ( Fig. 6A View FIGURE 6 ). Aedeagus basally a blunt triangle anteriorly directed, filiform posteriorly with nearly imperceptible spicules ( Fig. 6D View FIGURE 6 ). Tergum 10 ( Fig. 5B View FIGURE 5 ) wider than long, anterior margin with distinctive basolateral process, narrowly posteriorly, the posterior margin membranous, with two patches of submedial elongate setae.

Female. As in male but with the following differences: Head ( Fig. 1B View FIGURE 1 ). Clypeus pale yellow with 10 setae at disk. Antenna ( Fig. 1C View FIGURE 1 ) dark brown. Wing (3B), length 3.0 mm. Terminalia ( Fig. 4C View FIGURE 4 ): sternum 8 wider than long; tergum 9 dark brown, with anterior margin slightly emarginated, posterior margin rounded; sternum 9 forming a band with anterolateral projections; apically rounded, with dense minute spicules and moderately sized setae present. Segment 10 shorter than cerci, long than wider, V-shaped; cercus dark brown, longer than wide.

Distribution. This species is known only from the type locality Laguna de Santo Domingo, Huatusco, Veracruz, Mexico ( Fig. 7 View FIGURE 7 ).

Etymology. The specific epithet is derived from Nahualt language, abbreviation of the word “ atitlaj ”, meaning “in water”, referring to the collection location.

Remarks. This new species is distinguished from all other known species of Dixella   by the hammer-like apical lobe of the gonocoxite and flattened basally expanded gonostylus bearing a pair of apical processes. This species is most closely related to Dixella cumbrica Peters & Cook   from Baja California Sur (Sierra Laguna), sharing similar characteristics of body color, the shape of the apical lobe of the gonocoxite and flattened gonostylus. Dixella atitla   sp. nov. differs from D. cumbrica   (characters in parenthesis) in having: (1) fore coxa dark brown basally (hyaline); (2) femora yellowish with brown apices and tibiae pale brown, with brown apices (femora and tibiae light brown); (3) halter brown (hyaline); (4) wing not spotted (wing slightly spotted on r-m and base R 2+3); (5) scutellum with six setae (two weak setae); (6) apical lobe of the gonocoxite hammer-like (moderately long, thick, with stellate tip), and (7) gonostylus flattened, wider basally with a pair of processes (flat, simple).

The female is similar to male, with segment 10 longer than wide, V-shaped and shorter than cercus, which distinguishes it from other species for which females are known. The female of D. cumbrica   is unknown.


Collection of Aquatic Important Microorganisms