Medetera montserratensis, Runyon, 2020

Runyon, Justin B., 2020, The Dolichopodidae (Diptera) of Montserrat, West Indies, ZooKeys 966, pp. 57-151 : 57

Medetera montserratensis sp. nov. Figs 10 , 11 , 12 , 13

Type material.

Holotype, ♂ labelled: "WEST INDIES: MONTSERRAT/ Fogarty Ghaut (Soldiers)/ 16°46.41'N, 62°12.44'W / 21 June 2017, JB Runyon"; "HOLOTYPE/ ♂ Medetera / montserratensis / Runyon [red label]" (USNM, type number USNMENT01350609). Paratypes: Montserrat: 1 ♂, 1 ♀, same data as holotype; 10 ♂, Runaway Ghaut, 175 m, 16°45.43'N, 62°12.89'W, 23 June 2017, J.B. Runyon; 1 ♀, Jack Boy Hill (top), 480 m, 16°45.797'N, 62°10.886'W, 25 June 2017, J.B. Runyon (MTEC, USNM).

Description.

Male (Fig. 10 ). Body length 2.7-3.0 mm, wing length 2.5-2.8 × width 1.0-1.1 mm. Head: Face and frons metallic dark blue-violet to green with little to no pruinosity, clypeus with brown pruinosity. Palpus black, rounded, covered with short brown setae and one larger brown to black seta near apex. Proboscis black with relatively large yellowish setae along margin. Antenna black, scape and pedicel sometimes somewhat yellow-orange ventrally; first flagellomere short, blunt, somewhat compressed laterally; arista-like stylus apical, inserted in slight sinus. Lower postocular setae white to yellow-white. Thorax: Scutum dark metallic green with distinct violet reflections and slight grayish pruinosity, flattened area of posterior mesonotum reddish-copper; small setae yellow, large setae black; ca. 12 pairs of small yellow biseriate acrostichal setae that are not very distinct from numerous small setae covering anterior half of scutum, posterior-most pair of acrostichal setae diverging slightly; three pairs of large black dorsocentral setae; scutellum with two pairs of large black marginal setae, outer pair 3/4 as long as inner pair. Pleuron dark metallic bluish green with more grayish pruinosity than scutum; with 2-3 small yellow-brown to black setae on lower proepisternum. Legs: Coxae dark brown with extreme tips becoming yellowish, coxa II often somewhat yellowish laterally; with yellow-brown setae. Legs otherwise yellow. Femora I and II with row of longer yellow-brown pv setae apically; femur II with short yellow ventral setae on basal half; femur III with setae on dorsal half brown, those on ventral half yellow, 2-3 distinct erect yellow-brown setae along middle of anterior surface and many longer erect brown ad setae at base. Tibia I without distinct setae, dorsal setulae brown, ventral setulae yellow; tibia II with setulae yellow to brown, with paired black dorsal setae near 1/3, five small brown apical setae; tibia III with setulae and most larger setae usually yellow, rather small brown ad seta near 1/5 and at apex, 4-5 large usually yellow pd setae. Tarsus I (Fig. 11A ) with tarsomere I(2) flattened and broadened apically; tarsomere I(3) slightly longer than wide, rounded apically, concave on anterior surface; tarsomere I(4, 5) very small, combined length less than length of tarsomere I(3); tarsomere III(1) with minute black posterior spicule at base and several distinct small black apical setae. Ratios of tibia:tarsomeres: leg I: 36-20-10-11-2-4; leg II: 48-22-9-8-4-4; leg III: 64-12-24-16-6-5. Wing: Hyaline, oval, with brown veins. Vein R2+3 nearly straight; R4+5 curving slightly backwards on apical half of wing, approaching and nearly parallel near apex with M1 which curves distinctly forward beyond crossvein dm-cu; crossvein dm-cu slightly longer than last part of CuA1. Calypter white with yellow-white setae. Halter knob and stem white. Abdomen: Stout basally, rather abruptly tapered distally, with yellow setae, metallic green with copper reflections, obscured by little or no pruinosity. Sternites brown with many short pale yellow setae. Hypopygium (Fig. 12 ) on a peduncle created by segments VI and VII; tergite VI setose; segment VII dark brown with tergite setose, sternite bare and rather flattened ventrally and strongly sclerotized. Hypopygial foramen left basolateral. Sternite VIII relatively large, dark brown, forming a setose cap-like cover over hypopygial foramen. Epandrium elongate oval, 3 × as long as wide, brown dorsally and at base, becoming yellow ventrally, with two small ventral setae near apex. Surstylus yellow, with two large lobes; dorsal lobe with patch of sensilla and three or four small setae at apex; ventral lobe shallowly cordate apically, with large branched seta near 1/2 and finger-like medial lobe near base. Cercus yellow with yellow setae and hairs, rounded dorsally, rather flat ventrally, with small finger-like apical lobe. Phallus simple, narrow with round apex, slightly longer than hypandrium. Hypandrium arising near mid-length of epandrium, and forming hood over phallus, more sclerotized along ventral margin.

Female. Body length 3.1-3.2 mm, wing length 2.7-2.8 × width 1.1-1.2 mm. Similar to male, but tarsus I plain with ratios of tarsomeres: 18-10-7-3-4.

Etymology.

This species is named for the island of Montserrat.

Distribution.

Montserrat.

Remarks.

Medetera montserratensis belongs to the M. aberrans species group that is characterized in part by having tarsomeres I (2, 3) flattened and modified (for other group characters see Bickel and Arnaud 2011). The aberrans group contains 27 species in the Neotropics ( Yang et al. 2006, as Saccopheronta Becker), but only M. montserratensis , M. steyskali Robinson (Dominica), M. excavata (Becker) (Bolivia, Peru), and M. metallina (Becker) (Peru) have wholly yellow femora (the latter two species have “red-yellow” legs in contrast to the bright yellow legs of M. montserratensis and M. steyskali ). Medetera montserratensis and M. steyskali both are distinct from M. excavata which has an excavated tarsus I(3) ( Becker 1922: fig. 55) and M. metallina which has black postorbital setae. Medetera montserratensis is very similar to M. steyskali , and the two are likely sister taxa, but differs in having tarsomeres I (2, 3) broader (Fig. 11 ) and in small details in the shape of surstylar lobes (e.g., shape of the finger-like medial lobe).

Adults of Medetera montserratensis were found on trunks of large palm trees, several times seen occurring in small aggregations of 4-6 individuals that were mostly males (Fig. 13 ).

Figures

Figure 10. Medetera montserratensis sp. nov. habitus of male holotype, left lateral. Scale bar: 1.0 mm.

Figure 11. Tarsus I of males, posterior view A Medetera montserratensis sp. nov. B Medetera steyskali Robinson (Dominica). Scale bar: 0.25 mm.

Figure 12. Medetera montserratensis sp. nov. male terminalia, left lateral view. Abbreviations: epand-epandrium; hypand-hypandrium; T-tergite; S-sernite. Scale bar: 0.5 mm.

Figure 13. Medetera montserratensis sp. nov., group of four males on palm trunk in Runaway Ghaut, Montserrat, 23 June 2017. Photograph by Justin Runyon.