Dixella maculata Chaverri and Borkent, 2007

Chaverri, Luis Guillermo & Borkent, Art, 2007, The Meniscus midges of Costa Rica (Diptera: Dixidae), Zootaxa 1575 (1), pp. 1-34 : 4-10

Dixella maculata Chaverri and Borkent n. sp.

( Figures 1A , 2A , 4A , 6A , 7A , 10A , 15A , 18A )

Diagnosis. Male and female: only species of Dixidae in Central America with the wing with a distinctive brown spot over crossvein r-m ( Fig. 6A ). Also, male: only species of Dixidae in Central America with a thick apical peg at apex of the gonostylus ( Fig. 10A ).

Description. Male. Head ( Fig. 1A ): brown, with scattered spicules. Clypeus brown, short, 1.25 wider than long. Antennal scape yellowish, pedicel brown, flagellomeres light brown. Thorax ( Fig. 2A , 4A ): scutum with brown medial vitta extending from anterior margin to middle of scutum, broad anteriorly, narrow posteriorly; lateral vitta extending from supraalar area to near prescutal suture; anterolateral light brown spot connecting lateral and medial vittae; supraalar setae absent. Scutellum, mediotergite brown. Pleura with pronotum, propleuron, katepisternum, posterior anepisternum, anepimeron, metanepisternum dark brown; upper half of anepimeron yellowish. Wing ( Fig. 6A ; Table 1): dark spot over r-m; R 2+3 originating at r-m; stem of R 2+3 0.70 length of R 3. Halter: pale, 0.40 length of fore femur. Legs: coxae, trochanters yellowish; fore femur yellowish on basal 0.5, brown on apical 0.5; mid-, hind femora yellowish with apical portion brown; claws as figured ( Fig. 7A ). Genitalia ( Fig. 10A ): tergite 9 with anterior, posterior margins nearly straight, with scattered setae. Sternite 9 with posterior margin with narrow excavation, with 5–6 lateral elongate setae. Gonocoxite as long as wide; basal lobe not visible; anterior margin of apical lobe arising near midlength of gonocoxite, 1.20 as long as gonocoxite, bifid apically, with two short, strong subapical setae. Gonostylus evenly curved, apex with one thick, shorter spine, one slender elongate seta. Paramere straplike, sinuous, directed dorsally, apices convergent. Aedeagus slender curved band with ventrally directed medial flange. Tergite 10 pale, ventral margin rounded.

Female. As for male, with following differences: Wing: ( Table 2). Genitalia ( Fig. 15A ): sternite 8 wider than long, narrow anteriorly, lateral notch located on apical 0.5, posterior margin evenly curved; tergite 9 dark brown, with short, posterolateral lobe, short anteroventromedial margin with acute projection; sternite 9 anterior margin with notch, posteromedial margin projecting posteriorly; segment 10 as wide as cercus, posteromedial margin acute; cercus conical, dark brown, with dense minute spicules, moderately-sized setae.

Immatures. not described.

Distribution and bionomics. This species is known from Costa Rica and Panama at altitudes from 2000–2959 m ( Fig. 18A ) and adults were collected during the rainy season (August–September) in both countries. In Costa Rica, adults have been reared from pupae found in ground pools at 2400 and from pupae collected along margins of streams and marshy depressions in grazing areas. Larvae in Panama were found along a stream margin at 2150 m. All sites are in Tropical Lower Montane Rainforest and Tropical Montane Rainforest.

Taxonomic discussion. The male and female of this species were associated through a similar pigmentation pattern and were collected together as pupae in the same habitat from Valle del Silencio, Costa Rica. Unfortunately, the exuviae were subsequently lost. The wing of this species is nearly unique in the Neotropical Region. Dixella argentina Alexander , from Argentina, also has a large dark spot over r-m but R 2+3 is less than 0.7X the length of R 3, the medial vitta is wedge-shaped and the lateral vitta rounded.

Heinemann and Belkin (1977, 1978) recorded this species as Dixella sp. 3 with the following specimens in the USNM labeled as such: CR 315-11, 315-12, 315-13, 315-14, 315-15, 315-17, 315-18, 317-10, 379-10 and PA 1055-11, 1055-12, 1055-100, 101. The following additional specimens were labeled by Heinemann and Belkin as Dixella sp. 3 and may be members of D. maculata but, because there were no associated adults, could not be identified at this time: one fourth instar larva (CR315-10), one associated larval and pupal exuviae (CR315-16), five larval (PA1055-10, 13, 15-17), and one associated larval and pupal exuviae (PA1055- 14). Finally, Heinemann and Belkin (1977) recorded Dixella sp. 3 from their localities CR311 and CR312 and we did not examine any specimens from these samples (CR311 = 1.6 km N of turnoff to San Cristobal Norte, Cangreja; CR312 = 4.7 km NW of El Empalme, a site represented by other material we examined).

Types. Holotype, male adult on microscope slide, labeled “ HOLOTYPE Dixella maculata Chaverri and Borkent ”, “ Costa Rica, Prov. Limón, Talamanca, Bratsi, ACLA-P, Parque Internacional La Amistad , Valle del Silencio , 2476 m, 26-IX-2001, LS 341222 577399, G. Chaverri, LGCh 452" ( INBC) . Allotype, female adult on microscope slide, labeled as for holotype ( INBC) . Paratypes: 6♂, 2 ♀, on microscope slides, each with associated larval and pupal exuviae on separate slides: Costa Rica, Cartago, 4.7 km NW of El Empalme on Natl. Rt. 2, 2010 m, 1-VIII-1971, D.A. Schroeder ( USNM) ; 1♂, on microscope slide, with larval and pupal exuviae on separate slide, Costa Rica, Heredia, Cartagos, 7.9 km N of Rt. 125 junction on Natl. Rt .9, 2000 m, 19-VIII-1971, D.A. Schroeder ( USNM) ; 1 ♀, on microscope slide, Costa Rica, Limón, Talamanca, ACLA-P, Parque Internacional La Amistad, Cerro Kasir, 2959 m, 20-IX-2000, LS 349700 666850, Malaise trap, M. Alfaro ( CNCI) ; 2 ♀ on microscope slides, each with pupal exuviae on separate slides, 1♂, 1 ♀ on microscope slides, each with larval and pupal exuviae on separate slides, Panama, Chiriqui, Cerro Punta, 4km E of Cerro

Punta and 1.5km E of Bajo Grande on trail to Boquete, 2150 m, 14-IX-1971, D.A. Schroeder (USNM).

Derivation of specific epithet. The name maculata (spot) refers to the distinctive dark spot on r-m of the wing of adults of this species.

Figures

FIGURE 1. Head capsules of male Dixella, anterior view. (A) D. maculata; (B) D. hernandezi; (C) D. shannoni; (D) D. hansoni; (E) D. fernandezae; (F) D. jironi; (G) D. venezuelensis; (H) D. woodi; (I) D. lobata; (J) D. suzukii.

FIGURE 2. Thoraces of male Dixella, dorsal view. (A) D. maculata; (B) D. hernandezi; (C) D. shannoni; (D) D. hansoni.

FIGURE 4. Thoraces of male Dixella, lateral view. (A) D. maculata; (B) D. hernandezi; (C) D. shannoni; (D) D. hansoni.

FIGURE 6. Wings of male Dixella. (A) D. maculata; (B) D. hernandezi; (C) D. shannoni; (D) D. hansoni; (E) D. fernandezae; (F) D. jironi; (G) D. venezuelensis; (H) D. woodi; (I) D. lobata; (J) D. suzukii.

FIGURE 7. Claws of male Dixella. (A) D. maculata; (B) D. hernandezi; (C) D. shannoni; (D) D. hansoni.

FIGURE 10. Genitalia of male Dixella, dorsal view. (A) D. maculata; (B) D. hernandezi.

FIGURE 15. Genitalia of female Dixella, ventral view. (A) D. maculata; (B) D. shannoni.

FIGURE 18. Distributions of Dixella species in Costa Rica: (A) D. maculata—O; D. hernandezi–-#, D. shannoni— ; (B) D. hansoni—O, D. fernandezae—#, D. jironi— .