Scatella bicolor Mathis & Wirth 1981

Scatella (Neoscatella) bicolor

DIAGNOSIS.—Specimens of this species are most similar to those of S. albilutea and S. tasmaniae but may be distinguished from them and other congeners by the following combination of character states: frons uniformly and densely pollinose; anterior lacteroclinate fronto-orbital bristle generally shorter than posterior bristle; dorsum of interfoveal carina broadly explanate, not creased, with short median sulcus; distance between antennal bases about equal to combined length of second and third antennal segments; face of male deeply velvety brown on receding portion to just before oral margin which is yellowish gold; face of both sexes uniformly setulose with subequal small setulae except for one pair of large, slightly dorsally curved setae toward posteroventral angle; orientation of eye distinctly oblique to plane of oral margin; scutum grayish to brownish, lacking a distinct median stripe; brownish coloration of disc of scutellum darker than grayish brown coloration of scutum; setae of front coxa and femur similar in both sexes; tarsi yellowish, contrasting with gray coloration of femora and tibiae; first costal section of male wing thickened, emarginate posteriorly on apical half; most of male wing apicad of anterior crossvein brown, white area in cell R3 reduced, not extending more than one-half cell width, closely appressed to vein R2+3; apical white spot in cell R5 of female wing narrowly rectangular.

DESCRIPTION.—Small to moderately small shore flies, length 1.79 to 2.87 mm; mostly gray, but with considerable light brownish to yellowish coloration; almostly entirely pollinose, appearing dull.

Head (Figures 12–13): Head width-to-height ratio averaging 1 : 0.63; frons uniformly and entirely pollinose, appearing dull, mostly gray, but with very faint tannish to slightly bluish coloration, most specimens with some coloration distinction between mesofrons and parafrons, vertex usually faintly distinguished in color, mesofrons distinguished from parafrons by shallowly impressed sulcus; anterior lateroclinate fronto-or-bital bristles slightly smaller than posterior bristle, especially in males. Antenna mostly concolorous with mesofrons or slightly darker, third segment faintly yellowish to pinkish basally; third antennal segment subequal to slightly longer than combined length of first and second segments; arista appearing mostly bare, setae small, hairlike; distance between antennal bases large, usually greater than length of antenna. Coloration and conformation of face sexually dimorphic. Male: obviously explanate dorsally, with distinct anteromedian sulcus, angle between dorsal and anterior aspects of face more angulate; anterior aspect of face dark, velvety brown to yellowish oral margin, both colors contrasting with dorsum, which is mostly gray to faintly bluish gray. Female: moderately explanate dorsally; anterior aspect mostly lightly yellowish, contrasting only slightly with dorsum, which is mostly grayish, some specimens also with faint bluish to pinkish coloration. Facial setae in both sexes small, hairlike, inconspicuous except for 1 pair of larger, porrect to slightly upcurved bristles inserted toward posteroventral angle of face. Clypeus narrow, mostly concolorous with ventral margin of face. Eye broadly elliptical, more so in male, oriented at distinct, oblique angle to plane of epistomal margin; eye width-to-height ratio averaging 1 : 0.94; gena moderately high, eye-to-cheek ratio averaging 1 : 0.31.

Thorax (Figure 14): Coloration of male more contrasting and distinct. Mesonotum mostly gray but with distinct light brown to brown area between dorsocentral bristles and extending entire length, becoming fainter just before scutellum, scutellum coloration darker; humeral callus, notopleuron, and immediate area gray to faintly bluish gray, in male distinctly contrasting with surrounding coloration; mesopleuron and pteropleuron, especially in male, yellowish to brownish yellow, coloration becoming lighter posteriorly on pteropleuron, sternopleuron gradually becoming lighter. Legs concolorous; femora and tibiae gray, femoral-tibial articulation amber colored; tarsi yellowish, becoming darker apically but not distinctly blackish. Wings (Figures 8–9) sexually dimorphic; male wing differing as follows: Costa thickened, especially first costal section; infuscation much darker; white areas more narrowly defined; otherwise wing as described in diagnosis.

Abdomen: Mostly unicolorous; dorsum mostly gray, but with faint bluish to greenish coloration; lateral margins, especially on apical terga, with faint to fairly distinct brownish area. Male terminalia as in Figures 15–16.

TYPE MATERIAL.—Holotype male is labeled: “Narrabeen Lagoon NSW 12 Oct 1956 tidal flat/W. W. Wirth collector/HOLOTYPE Scatella (Neoscatella) bicolor Mathis & Wirth [handwritten, red].” Allotype female and 82 paratypes (52, 30) have the same label data as the holotype. Other paratypes as follows: NEW SOUTH WALES: BERMAGUI BEACH, 24 Nov 1974, Z. Liepa (12, 13; ANIC, USNM); COILA LAKE, Tuross Hds., 19 Jul 1973, Z. Liepa (17, 7; ANIC, USNM); DEE WHY, 24 Feb 1957, 31 Mar 1962, 4 Nov 1971, W. W. Wirth, D. K. McAlpine, G. A. Holloway (3, 7; AM, USNM); KURNELL, 3 May 1931, K. McKeown (1, 1; AM); LAKE CURALO, Eden, 3 Aug 1973, Z. Liepa (2; ANIC); POTATO POINT, 9.5 km E Bodalla, 20 Jul 1973, Z. Liepa (4, 6; ANIC, USNM); WALLAGA LAKE, 15–21 Jul 1973, Z. Liepa (6, 4; ANIC, USNM). WESTERN AUSTRALIA: THOMAS RIVER (estuary), Esperance District, 8 Nov 1977, Z. Liepa (3, 3; ANIC). The holotype, allotype, and some of the paratypes will be deposited in the Australian National Insect Collection, Canberra. The remaining paratopotypes will be in the National Museum of Natural History, Smithsonian Institution, Washington, D.C. The holotype specimen is double mounted (minute nadel in polyporus block) and is in excellent condition.

GEOGRAPHIC DISTRIBUTION (Figure 17).—Southern coast of New South Wales and south-central coast of Western Australia.

ETYMOLOGY.—The species epithet bicolor is of Latin derivation and means “two-colored,” referring to the two-toned face of specimens of this species.