Drosophila stylipennis, 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 : 47-48

publication ID

https://doi.org/ 10.1206/3859.1

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scientific name

Drosophila stylipennis

new species

Drosophila stylipennis , new species

Figures 2C View FIG ; 20 View FIG , 21B–D, F, G View FIG

DIAGNOSIS: A small to medium-sized species (thorax length ca. 0.86 mm [0.75–0.99]), light brown to yellowish species with a uniquely long, slender aedeagus, length 16.0× the greatest width; basal third of aedeagus strongly arched, aedeagal angle ca. 84°; distiphallus narrow in full ventral view, length 2.5× the width, with pair of slightly pointed lobes on proximal margin; surstylus with 7 pointed, thornlike prensisetae.

DESCRIPTION: Male: Head: Frontal index 1.08 (0.92–1.20), top to bottom width ratio 1.46 (1.33–1.64). Ocellar triangle slightly raised above rest of front, dark brown in middle, about 0.6× length of front. Frons uniform light brown to ochraceous in color, ocellar triangle and frontoorbital plates dull; frontal vitae golden, finely striate, shiny; margin around ptilinal suture ochre. Orbital setae dark brown with brassy highlights, or1:or3 ratio 0.91 (0.82–1.00), or2:or1 ratio 0.56 (0.50–0.66), postocellar setae 0.51 and ocellar setae 0.74× the frontal length; base of ocellar seta just within tangent between median and lateral ocelli; postocellar setae from nearly parallel to minutely crossed at tips; vt index 1.08 (1.04–1.13). Vibrissal index 0.38 (0.33–0.44). Face same color as front, edge of carina lighter. Carina low and narrow, greatest width slightly>0.5× width of pedicel; edge slightly flattened, without sulcus in Puerto Rican specimens, with sulcus in Dominican Republic specimens. Cheek index about 0.09. Eye index 1.48 (1.39–1.65). Occiput brown, pollinose. Antenna with flagellomere 1 same light brown to ochraceous as most of front; pedicel lighter; arista with 3–4 dorsal and 2 ventral branches, plus large terminal fork. Proboscis dark to light yellowish; palpus slightly lighter, with one apical and one subapical seta.

Thorax length 0.90 mm (0.77–0.99). Scutum light, dull brown ( Puerto Rico specimens) to ochraceous yellow ( Dominican Republic specimens); 6 rows of acrostichal setulae; pair of prescutellar setae from small to well differentiated: barely differentiated from acrostichals in holotype, 0.25× length of posterior dorsocentral setae, to 0.36–0.57× in other specimens; setae lateral to prescutellars undifferentiated from acrostichals; h index 0.91. Transverse distance of dorsocentral setae 2.49× (2.14–2.77) the longitudinal distance. Scutellum slightly lighter than scutum, dull; basal scutellars strongly convergent, apical scutellars crossing for about half their length; scut index 0.33 (0.25–0.40). Pleura slightly darker than scutum (dorsally more infuscate), slightly shiny, without pollinosity; sterno index 0.77 (0.64–0.89). Halter light brown. Legs dull yellowish.

Wing hyaline but slightly dusky; veins light brown, length 1.89 (1.43–2.24) mm. Indices: Wing index 2.40, C, 2.10; ac, 2.84 (2.60–3.00); hb, 0.52 (0.47–0.57); 4-C, 1.13 (1.06–1.18); 4V, 1.89 (1.81–2.00); 5x, 1.54 (1.33–1.70); M, 0.59 (0.54–0.65). Subcostal section of C with heavy spinules; wing tip slightly pointed, vein R 2+3 nearly straight (not slightly sinuous).

Abdomen overall color dark yellowish brown, posterior margins of tergites with diffuse, slightly darker transverse bands that grade into lighter areas.

Male terminalia (fig. 20): Epandrium with dense microtrichia, only ventral lobe with setae; ventral lobe small, apex blunt, barely extended beyond ventral margin of surstylus, with 5 setae. Cerci fused laterally to epandrium. Surstylus with abundant microtrichia; mesal margin of surstylus with row of 7 prensisetae pegs, about 7 ventral setae. Subepandrial sclerite (not examined).

Hypandrial shape from virtually rectangular with straight sides to more rounded (sides slightly convex), length 1.3× greatest width. Gonopods fused to hypandrium and aedeagal apodeme; seta at tip of lobe a minute spinule. Aedeagus distinctive: long, slender, length 16.0× the greatest width; basal third of aedeagus strongly arched, aedeagal angle 84°; distiphallus narrow in full ventral view, length 2.5× the width, with pair of slightly pointed lobes on proximal margin; base of aedeagus fused to aedeagal apodeme. Aedeagal apodeme short, keel shaped.

Female: General morphology similar to males. Measurements (based on specimen 13): Thorax length 0.75 mm. Frontal length 0.22 mm; top to bottom width ratio 1.41. or1:or3 ratio 1.00, or2:or1 ratio 0.50, postocellar setae 0.50 and ocellar setae 0.82× the frontal length, vt index 0.94. Cheek index 0.10. Eye index 1.53. Thorax length 0.75 mm. Prescutellar setae 0.57× length of posterior dorsocentral setae. Transverse distance of dorsocentral setae 2.45× the longitudinal distance. Scut index 0.88, sterno index 0.84. Wing length 1.69 mm. Wing indices: 4v 1.89; 5x 1.76; M, 0.62.

Female terminalia (figs. 21B–D, F,G): Valves of oviscapt of moderate length, length 2.46× greatest width in ventral view, tip rounded in lateral view, with 16 ovisensilla pegs. Spermathecal capsule small, cup shaped, height slightly less than greatest width; basal introvert reaching about 0.60× length of capsule.

TYPE: Holotype, ♂: “ PUERTO RICO, Mayaguez / Jul–Aug 1957, W.B. Heed. ” Type is point mounted, in good condition, abdomen removed and cleared, genitalia dissected by D.A.G. ( DBG 12 ) and stored in glass microvial on same pin as specimen. In AMNH.

OTHER SPECIMENS: Paratypes, 2 ♀♀ (one dissected, DBG 13), with same labels as holotype ( AMNH) . Nontypes : DOMINICAN REPUBLIC: “ La Vega Prov., 7.2 m S Constanza, rd to San José de Ocoa, 5000 ft., 29/VII/91, Grimaldi and Stark” (1♂, dissected by D.A.G., DBG 60) ( AMNH) ; “ Las Abejas [Pedernales Prov.] 1300 m, cloud for[est], sweep, 17.1.1989, J.E. Swann ” (1♂, dissected, DBG 51)( UGIC) .

ETYMOLOGY: Derived from stilus (L., a pointed instrument for writing on wax tablets, a stylus) and - pennis, a derivation of penis (Latin), in reference to the long, thin aedeagus.

COMMENTS: In the holotype (male) specimen of D. stylipennis the prescutellars are very small, barely differentiated from the acrostichals; in other specimens (including paratype female DBG 13, also from the type locality), the prescutellars are nearly twice the length of the holotype prescutellars. There are slight differences between males from Puerto Rico and the western Dominican Republic, the latter having a longer aedeagus with longer gonopods (possibly due to the 20% larger body size of the latter), and more rounded hypandrium. Dominican specimens are also lighter in body color, being yellow/ochraceous instead of light brown .


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