Distostylus irwini, Metz, Mark A. & Webb, Donald W., 2003

Metz, Mark A. & Webb, Donald W., 2003, Distostylus gen. nov., a monotypic therevine genus (Diptera: Asiloidea: Therevidae) from the Caribbean Island of Dominica, Zootaxa 222, pp. 1-12 : 6-9

Distostylus irwini spec. nov. Webb

Etymology. Named in honor of the therevidologist and collector of the specimens, Dr. Michael E. Irwin and used as a noun in apposition.

Description of male holotype (MEI 146471). Length 5.7 mm.

Head. Length 0.68 mm. Ocellar tubercle dark reddish brown, pruinescence gray; setae black, short. Eyes reddish brown, contiguous medially. Frons yellowish gray, becoming dark brown when specimen rotated clockwise; setae dark brown, short. Antenna 0.91 times length of head; dark brown, scape with dense gray pruinescence; scape length 0.21 mm, width 0.10 mm, 2.1 times longer than wide, 3.5 times length of pedicel, 0.8 times width of flagellum, setae dark reddish brown, grading into macrosetae; pedicel length 0.06 mm, width 0.08 mm, setae dark reddish brown, short; first flagellomere length 0.25 mm, 0.12 mm wide, second flagellomere length 0.04 mm, 0.03 mm wide, third flagellomere tapered posteriorly, length 0.0 6 mm, width 0.0 3 mm; flagellum length 0.35 mm, 2.9 times longer than wide, 1.7 times length of scape. Maxillary palpus dark reddish brown, pruinescence gray, length 0.38 mm, width 0.06 mm, 6.3 times longer than wide; setae pale yellow, elongate.

Thorax. Mesonotum dull brown in ground color, pruinescence dull greenish gray anteriorly; dorsocentral and lateral vittae dull brown; setae black, elongate, with scattered brownish gold setae laterally and pale iridescent turquoise lanceolate appressed setae. Pleura and scutellum dark brown, pruinescence dull gray; setae white, elongate on propleuron and dorsoanterior half of katepisternum, pale iridescent turquoise lanceolate setae on anepisternum and scutellum, whitish brown filiform setae on laterotergite. Wing. Membrane opaque, costal and subcostal veins dark yellow, other veins brown; length 4.7 mm, width 1.7 mm, 2.7 times longer than wide; pterostigma dark brown. Halter dark brown. Legs. Coxae dark brown, pruinescence gray; setae white. Femora dark brown, pruinescence gray; setae white, elongate, filiform on ventral half of fore femur, with mixture of pale brown and iridescent turquoise lanceolate, appressed setae on dorsal surface; 4:4:7 av, 0:0:3 pv. Tibiae and tarsi dark brown.

Abdomen. Dark reddish brown with gray pruinescence across posterior margin of tergite 1, a broad lateral pruinescent triangle on tergites 2­6 which extends across posterior margin of tergites, narrow on tergite 2 but increasing in width to tergite 6; tergite 7 covered with gray pruinescence; dorsal setae dark brown appressed on dark brown areas of tergites, white appressed on pruinescent areas of tergites, lateral setae white. Terminalia (paratype MEI 146969). Dark reddish brown. Tergite 8 ( Fig. 3 ) with setae dark yellow, scattered on lateral lobes. Sternite 8 ( Fig. 5 ) with anterior margin slightly rounded, posterior margin truncate; setae along posterolateral margin dark yellow, short. Epandrium ( Fig. 3 ) quadrate, posterolateral corners with narrow glabrous margin; setae dark brown. Cercus ( Fig. 3 ) oval, ending distal to apex of epandrium and above apex of hypoproct. Hypoproct ( Fig. 3 ) quadrate, posterior margin truncate, ending distal to apex of epandrium and below apex of cercus; ventral surface quadrate ( Fig. 4 ), extending anteriorly as two narrow sclerotized projections, then continuing as lightly sclerotized membrane; posterior area with several thick setae. Gonocoxite ventral view ( Fig. 5 ) with basal two­thirds quadrate, slightly rounded laterally, then tapering posteriorly to broad outer gonocoxal process; dorsal view ( Fig. 6 ) with inner gonocoxal process short, narrow with a single apical dark brown setae; lateral view ( Fig. 7 ) broadly tapered posteriorly, outer gonocoxal process ending distal to inner gonocoxal process; setae dark brown; ventral lobe ( Fig. 5 ) with several short spines on ventral surface. Gonostylus in lateral view ( Fig. 8 ) uniquely shaped, basodorsal lobe broad, truncate dorsally, slightly angled posteriorly with several pale yellow setae; apical half of gonostylus curved dorsomedially into a single tooth; apicoventral area of gonostylus enlarged, bulbous, with numerous dark reddish brown setae. Aedeagus in dorsal view ( Fig. 9 ) with dorsal apodeme oval, sides rounded; anterior margin emarginate; ventral apodeme ( Fig. 10 ) short, not reaching anterior margin of dorsal apodeme, anterior margin truncate, ventral surface with median keel; distiphallus in dorsal view ( Fig. 9 ) slightly expanded laterally at subapex, lateral view ( Fig. 11 ) decurved ventrally at 90º angle, with several small coarse serration's posterolaterally at apex; ejaculatory apodeme in dorsal view ( Fig. 9 ) with anterior half slightly expanded laterally, anterior margin truncate, extending beyond anterior margin of dorsal apodeme, in cross section ( Fig. 9 inset) flattened dorsoventrally; lateral ejaculatory process ( Figs. 9­10 ) large, heavily sclerotized, circular, separated medially into lateral halves.

Variation. Body length 4.8­6.2, 5.8 mm (N=10). Thoracic macrosetae na 3, sa 2a, pa 1, dc 2, sc 2 (N=10). Av macrosetae 2­5:3­6:6­10 (N=10), pv macrosetae 0:0:2­3 (N=10).

Description of female. Similar to male except for following. Length 5.3­6.3, 6.0 mm (N=10).

Head. Frons (when viewed frontally) dark brown over dorsal three­fourth, yellowish gray on ventral fourth (entirely yellowish gray when viewed dorsolaterally); setae dark brown, short.

Thorax. na 3, sa 2, pa 1, dc 2, sc 2 (N=10). Mesonotum dull brown in ground color, pruinescence dull greenish gray anteriorly; vittae dull brown; setae a mixture of black, short, scattered filiform setae with whitish turquoise iridescent lanceolate appressed setae over entire mesonotum. Legs. Femora with av macrosetae 2­7:2­5:6­9 (N=10), pv macrosetae 0:0:1­3 (N=10).

Abdomen. Dark reddish brown, subshiny, posterolateral area of tergites 1­7 with gray pruinescence; dorsal setae dark brown, appressed over dark brown areas of tergite 1­4, over entire surface of tergites 5­7 with white appressed lanceolate setae on posterior margin of tergite 1, separated medially, and with white filiform setae posterolaterally on tergites 2­3. Terminalia. Dark reddish brown. Penal guide ( Fig. 12 ) clavate anteriorly. Furca ( Fig. 13 ) length 0.40 mm, width 0.20 mm, 2.0 times longer than wide; posterior margin rounded, sides sinuate, anterior margin truncate. Common duct ( Fig. 13 ) shorter than furca. Accessory glands with two, independent openings to the bursa copulatrix ( Fig. 13 ).

Distribution. Distostylus irwini has only been collected on the island of Dominica.

Biology. Specimens of Distostylus irwini have been hand­netted on blossoms of beach pea [ Canavalia rosea (Swartz) A. P. Candolle ], or collected at light, or in a Malaise trap in a dry wash in a deciduous forest from 5 October to 20 March at elevations up to 100 m.

Specimens Examined (N=25). Type material. The holotype male (MEI 146471) of Distostylus irwini Webb was collected on the Island of Dominica, St. John Parish, Cabrits National Park [15.583º N, 61.472º W], in a Malaise trap in a dry deciduous forest, elevation 100 m, March 19­20, 2003, by M. E. Irwin, B. M. Shepard, E. Benson, G., & G. Carner, and is deposited in the California Academy of Sciences (type number 17900).

PARATYPES: DOMINICA. St. George Parish: Fond Colet, [15.315º N, 61.394º W], 5­5­X­1964, P. J. Spangler, 1 female MEI 0 40427 ( USNM). St. John Parish: same data as holotype, 2 males 2 females MEI 146445, 146473­4, 146478 (MEI), 1 male 1 female MEI 146975­6 ( CUCC); Cabrit Swamp, [5.583º N, 61.472º W], 3­XI­1964, P. J. Spangler, 1 female MEI 0 40425 ( USNM). St. Joseph Parish: Clarke Hall, [15.4º N, 61.4º W], 12­III­1964, D. F. Bray, 1 male MEI 0 40428 ( USNM), on yellow blossom of beach pea [ Canavalia rosea ]; Macoucheri [Estate], [15.422º N, 61.439º W], 12­II­1965, W. W. Wirth, 1 female MEI 0 40424 ( USNM), at light; 14­II­1965, H. Evans, 1 female MEI 0 40426 ( USNM). St. Mark Parish: 1 km S Pointe Guignard, (15.243º N, 61.372º W), 17­ 19­III­ 2003, 100 m, M. E. Irwin, B. M. Shepard, E. Benson, & G. Carner, 1 female MEI 146692 ( CASC), 1 female MEI 146479 (MEI), 1 female 146908 ( INHS); 4 km N Soufriere, [15.238º N, 61.367° W], 75 m, 17­19­III­2003, M. E. Irwin, B. M. Shepard, E. Benson, & G. Carner, 2 females MEI 146472, 146477 ( CUCC), Malaise trap in dry wash of deciduous forest. St. Peter Parish: Anse Mulâtre Ravine, 2 km S Dublanc [15.505º N, 61.463º W], 15­19­III­2003, 50 m, M. E. Irwin, B. M. Shepard, E. Benson, & G. Carner, 1 male MEI 146961 ( INHS), 7 males MEI 146963, 146967, 146969, 146973, 146974, 146978, 146989 ( CUCC).

Figures

FIGURES 3 ­ 13. Distostylus irwini n. sp. 3. Tergite 8, epandrium, cerci, and hypoproct, dorsal view. 4. Epandrium, hypoproct ventral view. 5. Sternite 8, hypandrium, and gonocoxite ventral view. 6. Gonocoxite and hypandrium dorsal view. 7. Gonocoxite left lateral view. 8. Gonostylus right lateral view. 9. Aedeagus dorsal view (inset ejaculatory apodeme cross section). 10. Aedeagus ventral view (inset ventral apodeme cross section). 11. Aedeagus lateral. 12. Female sternite 8. 13. Female internal reproductive organs. Scale = 0.1 mm. Abbreviations: Acc = accessory gland duct, C = cercus, CD = common duct, DA = dorsal apodeme, Dp = distiphallus, EA = ejaculatory apodeme, Epa = epandrium, F = furca, GA = gonocoxal apodeme, Gs = gonostylus, Gx = gonocoxite, H = hypandrium, Hpt = hypoproct, IGP = inner gonocoxal process, LEP = lateral ejaculatory process, PG = penal guide, Sp = spermatheca, SpD = spermathecal duct, SpS = spermathecal sac, SS = sensory seta, S 8 = sternite 8, T 8 = tergite 8, VA = ventral apodeme, VL = ventral lobe.