Drosophila sevensteri, Grimaldi, 2016

Grimaldi, David A., 2016, Revision of the Drosophila bromeliae Species Group (Diptera: Drosophilidae): Central American, Caribbean, and Andean Species, American Museum Novitates 2016 (3859), pp. 1-56 : 31-34

Drosophila sevensteri , new species

Figures 12D–F

DIAGNOSIS: A medium-sized (thorax length 0.81–1.04 mm), brownish yellow species; frontal vitta darker (orange) than surrounding portions of front (yellowish); prescutellars consistently ≤ ca. 0.5× posterior dorsocentrals, no lateral pair; basal scutellar setae parallel; aedeagus of moderate thickness (length 5.5× the width), with significant curvature in lateral view; distiphallus large, bulbous, length 0.5× that of aedeagal shaft; surstylus with 8–9 short prensisetae, ventral setae of surstylus not sclerotized, two of these setae stout, spinelike; surstylus virtually bare of microtrichia; hypandrium trapezoidal, base broad.

DESCRIPTION: Male: Head: Frontal length 0.29 mm; frontal index (not measureable). Ocellar triangle barely raised above rest of front, dark brown between ocelli, anterior tip extended to about 0.6× the frontal length. Orbital setae dark brown, slightly brassy (not black), or1:or3 ratio 1.0, or2:or1 ratio 0.54, postocellar setae small 0.37×, ocellar setae 0.62× frontal length, bases of ocellar setae lying just outside tangent between median and lateral ocelli; postocellars slightly crossed at tips; vt index 1.0. Ocellar triangle and fronto-orbital plate dull, ochraceous yellow; frontal vitta darker, bronze, slightly shiny and finely striate. Vibrissal index 0.47. Face same color as most of dull parts of front, carina edge slightly lighter. Carina narrow, short, edge flattened, without sulcus. Cheek index 0.10. Eye index 1.36. Occiput light brown. Antenna with pedicel same color as frontal vitta, flagellomere 1 lighter; arista with 4 dorsal and 2 ventral branches, plus short terminal fork. Proboscis and clypeus slightly darker than face/front; palps lighter, each with one apical and one subapical seta.

Thorax length 0.81 mm (holotype ♂). Scutum ochraceous, dull; 6–8 irregular rows of acrostichal setulae. One pair of prescutellar setae, about 0.52× the length of posterior dorsocentral setae; setae lateral to prescutellars not differentiated from acrostichals; h index 0.84. Transverse/longitudinal distances of dorsocentral setae (dc index) (not measureable). Scutellum slightly lighter than scutum; basal scutellars parallel, apical scutellars crossing for ca. 0.5× their length; scut index 0.88. Pleura about same color as scutum (slightly darker dorsally), sterno index 0.86. Halter light, yellowish. Legs light, without darker/infuscate areas.

Wing hyaline, veins yellowish, length 2.01 mm, length to width ratio 2.21. Indices: C, 2.32; ac, 2.20; hb, 0.66, 4-C, 1.02; 4V, 1.76; 5x, 1.41; M, 0.56. Subcostal section of C with strong spinules on apical half only, wing tip rounded, vein R 2+3 nearly straight (not slightly sinuous).

Abdomen overall light ochraceous yellow, posterior margins of tergites faintly diffuse brown graded into lighter color.

Male terminalia (figs. 12D–F). Epandrium with just microtrichia, long setae only on ventral lobe; ventral lobe small, slender, with 4–5 setae, apex acute but not pointed. Cerci fused laterally to epandrium. Surstylus virtually bare of microtrichia, medial margin with row of 9 short prensisetae pegs (lengths only ca. 2–3× the width), about 8 ventral setae, 2 lateral ones stout and spinelike, none are sclerotized. Hypandrium trapezoidal, length 1.05× greatest width. Gonopods fused to hypandrium and aedeagal apodeme; apical seta fine, approximately 0.5× length of gonopod. Aedeagus of moderate thickness (length 5.5× the width), with significant curvature in lateral view, aedeagal angle 114°; distiphallus large, bulbous, length 0.5× length of aedeagal shaft, suboval in fully ventral view (apex slightly narrower). Aedeagal apodeme short, keel shaped.

Female: General morphology similar to males. Measurements based on dissected ♀ paratype ( DBG 18 ): Frontal length 0.32 mm; top to bottom width ratio (not measureable). Ocellar triangle about 0.6× the frontal length; or1:or3 ratio 1.0, or2:or1 ratio 0.58, postocellar seta 0.42× and ocellar seta 0.68× frontal length, vt index 1.0. Vibrissal index 0.53. Cheek index 0.09. Eye index 1.38. Thorax length 1.04 mm. Prescutellar setae 0.46× the length of posterior dorsocentral setae; h index 0.85; dc index not measureable; scut index 0.96, sterno index 0.83. Wing length 2.01 mm, length to width ratio 2.23. Wing indices: C, 2.08; ac, 2.72; hb, 0.57; 4-C, 1.22; 4v 2.12; 5x 1.76; M, 0.75 .

Female terminalia: Valves of oviscapt rounded at tip in lateral view, ca. 320 µm long, with 17–19 ovisensilla pegs; length of oviscapt 2.90× the greatest width in ventral view. Spermatheca cup shaped, height 1.00× the greatest width; basal introvert 0.73× the length of capsule.

TYPE: Holotype, ♂: “ PANAMA: Gatun L[ake], Barro Colorado Is. 8F/Jan Sevenster no. 39:HY/bred from Hibiscus flower.” Abdomen removed, cleared, genitalia dissected by D.A.G. ( DBG 20 ) and stored in a glass microvial on same pin as specimen. In AMNH.

OTHER SPECIMENS: Three paratypes (2♀♀, 1♂) same data as holotype, two dissected by D.A.G. ( DBG 17♂, 18♀). Portions of all specimens collapsed during drying, thus preventing some measurements. In AMNH .

ETYMOLOGY: Patronym for Jan Sevenster, in recognition of his collection of the type series and for his excellent monograph on the ecology of fruit-breeding drosophilids ( Sevenster, 1992).

COMMENTS: This species is one of five Central American members in the bromeliae complex, all with very similar male and female genitalia. It is most reliably distinguished, as described in the diagnosis, on the basis of greater curvature of the aedeagus, bulbous distiphallus, and surstylus virtually bare of microtrichia and having short prensisetae. Female terminalia are essentially indistinguishable from most other species in the complex; it was only on the basis of the type series of specimens having been reared from the same flower that the sexes could be associated.

Figures

FIG. 12. Male genitalia of two bromeliae group species. A–C. Drosophila billheedi, n. sp. (DBG 2, holotype). D–F. Drosophila sevensteri, n. sp. (DBG 20). A, D. Lateral views of aedeagus, aedeagal apodeme, gonopod, and full ventral view of distiphallus. B, E. Hypandria. C, F. Surstyli and ventral lobes of epandrium.