Setacera aldrichi Cresson 1935

Setacera aldrichi Cresson

Setacera aldrichi Cresson, 1935:348.—Sturtevant and Wheeler, 1954:202, 203 [key and locality data].—Wirth and Stone, 1956:472 [key].—Wirth, 1965:754 [nearctic catalog].—Cole, 1969:402 [locality data].

DESCRIPTION.—Medium-sized to moderately large shore flies, length 3.84 to 4.92 mm; dorsum darkly olivaceous brown to mostly greenish, becoming grayer, duller ventrally.

Head (Figure 75): Head width-to-height ratio averaging 1 : 0.64; frons width-to-length ratio averaging 1 : 0.48; mesofrons and fronto-orbits deeply blue to greenish blue, dorsum of interfoveal carina more greenish blue, slightly lighter than mesofrons; shape of face sexually dimorphic, dorsal surface of male longer than height of anterior surface, subexplanate, anterior facial ridge broadly rounded, antennal foveae only slightly lower than dorsum, female with dorsal surface about equal to anterior surface, not subexplanate, antennal foveae inclinate; facial angle about 110°; anterior surface of face golden brown dorsally, becoming silvery white ventrally. Eye height-to-width ratio averaging 1 : 0.98; eye-to-cheek ratio averaging 1 : 0.43.

Thorax: Midtibia of male with dense patch of short setae ventroapically; costal vein ratio averaging 1 : 0.28; M1+2 vein ratio averaging 1 : 0.83.

Abdomen (Figure 78): Male terminalia (Figures 76, 77, 79) as in species group description. Female terminalia (Figures 80, 81) as in species group description.

TYPE MATERIAL.—The male holotype is labeled “Potlatch Ida[ho] VI. 20. 07. [20 Jun 1907; J. M. Aldrich collector]/ TYPE No. 6515 Setacera ALDRICHI E. T. Creson, Jr, [red].” The holotype is in the Academy of Natural Sciences of Philadelphia, ANSP 6515. Cresson's original description lists a female paratopotype that is also in the Academy's collection. The holotype specimen is directly pinned and is in good condition.

OTHER SPECIMENS EXAMINED.—CANADA. British Columbia: Clayton, 9 Aug 1917, A. L. Melander (2; USNM UNITED STATES. California: Mono Co., Mammoth Lakes, 29 Jul 1940, L. C. Kuitert (1; SU Idaho: Latah Co., Moscow, J. M. Aldrich (1; USNM); Moscow, Lake Merton, 2 Mar 1911, J. M. Aldrich (1 USNM); Potlach, 20 Jun 1907, J. M. Aldrich (1, 1; ANSP, USNM Nez Perce Co., Lewiston, 22 Jun 1968, R. Sanders (1; WSU Oregon: Grant Co., Seneca, 4.8 mi S, 17 Jun 1972, W. N. Mathis (5, 5; USNM Union Co., Ladd Canyon, 14 mi S LaGrande, 4250 ft, pond, 30 Jul 1977, R. S. Zack, E. J. Davis (3; USNM Utah: Rich Co., Garden City, 9 Aug 1967, G. F. Knowlton (1; USNM Washington: Clallam Co., Sequim, 25 Aug 1910 (1; ANSP Grant Co., O'Sullivan Dam, 4–5 Apr 1956, H. G. Davis (1; WSU Whitcam Co., Steptoe Canyon, 10 mi SW Pullman, 19 Feb 1977, W. J. Turner (1; USNM Wyoming: Lincoln Co., Kemmerer, 14 Aug 1950, A. H. Sturtevant (1, 1 USNM Teton Co., Yellowstone Park Lake, 18 Jul 1923, A. L. Melander (1; ANSP

DISTRIBUTION (Figure 82—Western North America between 110° and 128° west longitude and 37° and 53° north latitude.

NATURAL HISTORY.—I have collected specimens of S. aldrichi by sweeping emergent vegetation near the shore of a small backwater area of a mountain stream. Label data accompanying borrowed specimens that I examined indicate that the species also occurs on or near lakes and ponds.

The pacifica Group

SPECIES INCLUDED.—Setacera durani Cresson; S. jamesi, new species; S. needhami Johannsen; S. pacifica (Cresson); S. pilicornis (Coquillett); and S. trichoscelis, new species.

DIAGNOSIS.—Specimens of the pacifica group may be distinguished by the following combination of characters: antennal foveae sparsely tomentose, subshiny, nearly concolorous with dorsum of interfoveal carina and with similar metallic luster; vertico-orbits with velvety tomentose band very narrow, inconspicuous; posthumeral bristle well developed, subequal or slightly weaker than posterior notopleural bristle, distance between it and presutural bristle slightly less than that between notopleural bristles; fore- and midtibiae mostly dark and concolorous with femora, at most with tibial-femoral articulation pale; 5th tergum of male longer than either 3rd or 4th, narrowly to bluntly rounded, width at apex much less than length; 3rd and 4th sterna of male usually with dense patch of stout setae toward posterior margin, secondarily reduced in some species (S. needhami and S. trichoscelis

Male Terminalia: Epandrium subtriangular in posterior view, much narrower dorsally than ventrally, dorsum narrowly rounded, becoming gradually broader, truncate ventrally, lacking median sulcus (S. pacifica with superficially indication); cerci almost as wide as high in lateral view, with anteroposterior orientation; surstyli broadly fused basally (best seen in posterior view), usually with lateral and sometimes with median projections (shape diagnostic at species level), apically curved anteriorly in lateral view; gonite with pronglike projections, conformation and arrangement differing with species; aedeagus bluntly rounded apically; hypandrium with 1–2 projections, at least partially and usually mostly well sclerotized.

Female Terminalia: 7th tergum variable; 8th tergite comparatively short, almost as wide as high in some species, shape of dorsum in lateral view varying with species; 8th sternites elongate, 4 or more times longer than wide; 9th sternites vertically oriented, projecting posteriorly, well sclerotized, forming 2 conical projections; 9th sternal bristles borne at apex of 9th sternal projections, 2 large bristles on each, these approximate, often difficult to distinguish; female ventral receptacle with operculum as high as wide, subtrapezoidal to dome-shaped in lateral view, extending process with cervix as long as corpus, more or less paralled sided, juncture of cervix and corpus indicated on inner surface of curvature by small, lateral indentation, forming budlike projection in lateral view, curvature of corpus wide, open.

DISTRIBUTION.—New World. Except for S. trichoscelis, this species group is North American, mostly occurring west of the 100° meridian. An obvious exception is S. pilicornis, which occurs in southeastern United States and in Mexico.

NATURAL HISTORY.—Adults are generally associated with lentic aquatic systems, usually where algal mats have accumulated on the water's surface. Only the larva and puparium of S. needhami have been described (Johannson, 1935