Lamproscatella nivosa Cresson 1935

Lamproscatella (Haloscatella) nivosa Cresson

Lamproscatella nivosa Cresson, 1935:361.—Wirth and Stone, 1956:475 [key, distribution in California].—Wirth, 1965:756 [catalog].

Scatella (Lamproscatella) nivosa Sturtevant and Wheeler, 1954:175.

DIAGNOSIS.—Lamproscatella nivosa is allied with L. arichaeta and L. cephalotes but may be distinguished from these and other congeners by the following combination of characters: Mesofrons dull, generally completely pollinose, contrasting little from parafrons in texture, although often slightly more brownish in coloration; conformation of structures of male terminalia unique (Figures 19–20).

DESCRIPTION.—Small to moderately small shore flies, length 1.60 to 2.26 mm (averaging 1.95 mm); mostly pollinose, coloration gray but with faint brownish gray areas on dorsum.

Head (Figure 18): Head width-to-height ratio averaging 1:0.76; coloration generally charcoal gray to faintly brownish white. Mesofrons dull, pollinose, broadly rounded anteriorly, usually light brownish gray, contrasting with paler whitish gray parafrons; 3–4 small setae along anterior margin. First and third fronto-orbital setae much reduced, first seta slightly larger; third inserted approximately in line with other fronto-orbital setae, much closer to second than to fourth. Postocular seta just posterolaterad of divergent vertical bristle; 1–3 pair of divergent postocellar setae. Antenna dark, mostly black, pollinose; arista approximately equal to combined length of second and third antennal segments, pubescent to macropubescent. Face light brownish gray, distinctly protruding and arched, setose. Usually 3 pair of larger lateral facial setae, these becoming larger and more dorsally-curved toward posteroventral angle of face. Eye-to-cheek ratio averaging 1:0.55; gena generally concolorous with face or slightly lighter in color.

Thorax: Mesonotum light brown, pollinose, grayer toward lateral margins; scutellum generally lighter gray; setation moderately well developed. Pleural areas and legs grayer than dorsum; basitarsi often pale, yellowish orange; apical tarsomeres darker, mostly blackish: Wing slightly opaque, lac-teous; costal margin only slightly setose; costal veinratio averaging 1:0.16; M1+2 vein ratio averaging 1:0.54; posterior crossvein slightly angulate laterally, appearing wrinkled near middle.

Abdomen: Dorsum grayer than that of thorax, but with some brownish coloration toward anterior and posterior margins. Structures of male terminalia very distinctive; cerci and cercal cavity small, situated toward dorsal margin; fused surstyli widely separated, narrowly fingerlike, setulose, and with small emarginate bump between; aedeagus large, broad, extending from ventral margin of epandrium (Figures 19–20).

TYPE MATERIAL.—Holotype male is labeled: “/40 m N of Lusk, Wyo Jul, '95./Property of U of K [Snow Entomological Museum] On Deposit [pink]/269/Presumed HOLOTYPE Lamproscatella nivosa Cresson by W. N. Mathis [red].” The specimen is double mounted and the abdomen has been removed and dissected; the structures are in an attached microvial. The holotype will be deposited in the Snow Entomological Museum, The University of Kansas, Lawrence.

SPECIMENS EXAMINED.—CANADA: ALBERTA: Okotoks, Sheep River, 27 Jun 1968, W. W. Wirth (1 ; USNM). MANITOBA: Ninette, 16 May 1958, J. F. McAlpine (1 ; CNC), Russell, 1 Aug 1937, R. H. Beamer (KU). UNITED STATES: CALIFORNIA: Modoc Co., Jul 1948, 13 Aug 1948, W. W. Wirth (1 , 6 ; USNM), Lake City, 11 Oct 1952, E. I. Schlinger and J. Hall (1 ; UCR), Topaz Lake, 18 Aug, W. W. Wirth (1 ; USNM). NEVADA: Elko Co., Elko, 19 May 1926, M. C. VanDuzee (1 ; CAS); Humboldt Co., Denio, 11.3 km W, 23 Jun 1971, G. Steyskal (3 , 4 ; USNM); Lander Co., Austin, 8.1 km ESE, 5 Aug 1964, H. B. Leech (1 ; USNM); Washoe Co., Pyramid Lake, 28 Mar 1952, I. LaRivers (2 , 1 ; USNM). NORTH DAKOTA: Mountrail Co., White Lake, 8 Jun 1969, W. W. Wirth (5 , 6 ; USNM); Pierce Co., Pleasant Lake, Jun 1969, W. W. Wirth (4 , 14 ; USNM); Ramsey Co., Devil's Lake, 30 Jun 1921, C. K. Sibley (1 ; USNM). OREGON: Baker Co., Anthony Lake, 8 Jul 1977, R. S. and V. L. Zack (1 ; WSU); Harney Co., Borax Lake, 7.2 km NE Fields, 29 Jul 1975, W. N. Mathis (2 , 13 ; USNM), Harney Lake, hot spring, 25 May 1969, 16 Jun 1972, K. Goeden, W. N. Mathis (4 , 3 ; OSDA, USNM); Lake Co., Lake Abert, 19 Jun 1954, A. H. Sturtevant (1 ; USNM), Goose Lake State Park, 23 Aug 1970, K. W. Simpson (5 , 16 ; CU, USNM), Summer Lake, 25 Sep 1971, W. N. Mathis (31 , 114 ; USNM). UTAH: Tooele Co., Blue Lake, 27.4 km S Wendover, 26 Aug 1970 (1 ; CU). WASHINGTON: Grant Co., Soap Lake, 20 Aug 1922, A. L. Melander (2 , 1 ; USNM).

GEOGRAPHIC DISTRIBUTION (Figure 21).—This species occurs in western North America, primarily west of the 100th meridian between 38° and 52° north latitude.

DISTRIBUTION.—Both species of this subgenus are known to occur only along the coasts of the temperate and arctic Holarctic Region. Lamproscatella quadrisetosa is found in both the Palearctic and Nearctic Regions, whereas L. lattini is somewhat more restricted, occurring along the coast of western North America where there is exposure to the Pacific or Arctic Oceans. The range of the species apparently do not overlap, however.

NATURAL HISTORY.—The ecology, life cycle, and natural history of the species of Thinoscatella are not well known; neither have the immature stages of either species been described. Adults are common inhabitants of mud-sand beaches and at low tide they can be observed in considerable numbers among seaweed that has washed ashore. Adults also seem to prefer the mud-sand beaches of embayments or other protected estuary-like areas and are not found commonly where the tidal zone has direct exposure to the ocean and the constant churning action of large ocean waves. The maritime biotope has been called “the watt” by Dahl (1959:13), which he defines as follows:

Of biotopes belonging to the tidal zone of the sea, the watt may be characterized as a biotope regularly inundated by flood, consisting of a flat, silt-impregnated sand area, often crossed by waterfilled erosion grooves during low water. Bluegreen algae dominate the vegetation, further [sic] almost exclusively may consist of Salicornia.