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Text used courtesy of the Illinois Natural History Survey from:
LaBerge, W. E., Thorp, R. W., 2005. A revision of the bees of the genus Andrena of the Western Hemisphere. Part XIV. Subgenus Onagrandrena. Illinois Natural History Survey Bulletin 37: 1-63.
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Andrena omninigra females are distinctive in the extremely short dorsal thoracic vestiture and the deeply infumate, blackened wing membranes. The male of omninigra can be recognized by having black or dark brown hairs mixed with the pale on the thoracic dorsum and by having a tall vertex (above lateral ocellus vertex equals more than one ocellar diameter).
FEMALE: MEASUREMENTS AND RATIOS. — N = 20; length, 11-13 mm; width, 3-4 mm; WL, M = 4.45 ± 0.496 mm; FL/FW, M = 1.07 ± 0.009; FOVL/FOVW, M = 3.15 ± 0.058.
DIAGNOSIS. Vestiture black; wing membranes deeply infumate, dark brown, veins black; metasomal terga black without violaceous reflections. Galeae moderately long, moderately shiny, dulled by fine shagreening. Labral process longer than half length of labrum, narrowed apically, lateral edges strongly concave, apical part narrower than scape base. Clypeus with round punctures crowded except in narrow medial impunctate line, surface shiny; vertex above lateral ocellus equals slightly more than one ocellar diameter. Pronotum without humeral angle or vertical ridge. Mesoscutum and scutellum punctate, punctures crowded, interpunctural surfaces moderately dulled by fine shagreening. Propodeum with distinct dorsal surface; dorsal enclosure coarsely rugulate, rugulae mostly longitudinal except irregular basally; surface outside of enclosure punctatorugose, surfaces shagreened or finely tessellate. Mesepisternum distinctly punctate, interpunctural spaces moderately shiny, shagreened. Metasomal terga with abundant round punctures separated mostly by half to one puncture width or slightly more, apices of terga narrowly impunctate; surfaces shiny, unshagreened. Thoracic dorsum with hairs extremely short, almost scale-like, shorter than width of antennal scape; propodeum with lateral surface with abundant, moderately short, simple, erect hairs, dorsal margin with moderately long plumose hairs no longer than twice length of internal hairs and often less; scopal hairs long, simple, moderately abundant.
MALE: MEASUREMENTS AND RATIOS. — N = 20; length, 9-12 mm; width, 2-3 mm; WL, M = 3.92 ± 0.385 mm; FL/FW, M = 1.11 ± 0.008; FS1/FS2, M = 1.44 ± 0.026.
DIAGNOSIS. Vestiture color black except as follows: head with vestiture white except face above antennal fossae, along inner margins eyes, at least upper three-fourths of genal area with black hairs or white and black mixed. Thoracic hairs white to pale ochraceous except as follows: pronotum with some dark hairs especially above; mesoscutum with large patch of dark hairs or mixed white and black; scutellum usually with small medial patch of dark hairs or mixed; mesepipleuron and propodeum usually with black hairs mixed with white; tegulae with dark hairs. Tergal hairs black except basally on tergum 1 to 4 white (often terga 2, 3, with various amounts of black or brown and white hairs mixed), terga 5, 6, and 7 entirely black; sternal hairs from mostly white to mostly black; leg hairs on tibiae and tarsi black, basal segments black or mixed white and black. Wings distinctly infumate, but less than in female. Metasomal terga with coarse, round punctures separated mostly by one to two puncture widths; apical rims narrowly impunctate; surfaces unshagreened, shiny. Galeae as in female; labral process strongly reflexed, deeply emarginate apically, broad; clypeus as in female but usually without median impunctate line; vertex above lateral ocellus equals distinctly more than one ocellar diameter; flagellar segment 1 distinctly longer than segment 2, antennae relatively short. Pronotum as in female; mesoscutum as in female but punctures finer; propodeum sculptured as in female but dorsal enclosure with rugulae slightly finer. Metasomal terga 2-5 with apical areas shiny, with deep round punctures in basal three-fifths to two-thirds; basal areas slightly more sparsely punctate, shiny. Metasomal tergum 2 with basal area hairs at least half as long as those of tergum 1. Hind tibiae with outer surface hairs moderately long, distinctly shorter than dorsal femoral hairs. Sternum 7 as in linsleyana but hairs abundant, short; sternum 8 distinctly capitate apically, not at all emarginate (Figs. 23 and 24).
TYPE MATERIAL. The holotype female of A. (O.) omninigra (CAS No. 4,046) was collected in California by E. Norton. The holotype female of A. (O.) grundeli (CAS No. 4,233) was collected from Nippinawasse (near Midway), Madera Co., California, May 22, 1931, by E. S. Ross. The holotype female of A. (O.) clarkiae (CAS No. 6,706) was collected from Arroyo Seco, Monterey Co., California, May 21, 1955, by P. Torchio.
DISTRIBUTION. Andrena omninigra is known (Fig. 3) only from California (MacSwain, Raven, and Thorp, 1993, p. 13). The flight period for omninigra is late May to early July, males primarily in May, females primarily in early June. One record of a female in early March may be in error. A total of 293 females and 123 males were examined from localities listed below.
CALIFORNIA. BUTTE CO.: Arch Rock Tunnel (Highway 70, Feather River Canyon); Highway 70 (5 mi. W Butte-Plumas county line). CALAVERAS CO.: Mokelumne Hill; Railroad Flat (1.5 mi. E and 4 mi. S). CONTRA COSTA CO.: Antioch. EL DORADO CO.: Camino; Pollock Pines; Riverton; Snowline Camp. FRESNO CO.: Bass Lake (and 2 mi. E.); Kings Canyon (Ten-mile Creek); Sequoia National Forest (T13S, R26E, 7.8 mi. N Highway 180); Tollhouse (1.5 mi. W). KERN CO.: Bodfish (2 mi. S); Glenville (6.2 mi. E). LOS ANGELES CO.: Angeles Canyon; San Antonio Canyon. MADERA CO.: Nippinawasse (near Midway); North Fork (2.7 and 4.8 mi. N); Oakhurst. MARIPOSA CO.: El Portal; Mariposa (and 6 mi. S); Mormon Bar (2.8 mi. S and 6.5 mi. SW); Wawona; Yosemite Valley. MONTEREY CO.: Arroyo Seco; Arroyo Seco Camp. PLUMAS CO.: Elephant Butte (1 mi. N); Elephant Butte Tunnel (2.3 mi. E); Rock Creek (Jet. Highway 70, Feather River Canyon). SACRAMENTO CO.: Folsom. SAN BENITO CO.: Hollister. SAN DIEGO CO.: Mt. Laguna. SAN LUIS OBSIPO CO.: Santa Margarita (5 mi. NE). SANTA CRUZ CO.: Felton. SOLANO/YOLO CO.: Putah Canyon. TULARE CO.: California Hot Springs; Kaweah; Pine Flat (3.7 mi. SE); Sequoia National Park. TUOLUMNE CO.: 3, 500 feet alt.; Buck Meadows-Mather; Strawberry; Twain Harte (4 mi. W).
BIOLOGY. — Linsley (1972) records robber flies, Callinicus calcaneus, as predators on A. omninigra in early June 1970 near Railroad Flat, Calaveras County, California, while female bees were nectaring at flowers of mountain misery, Chaemaebatia foliolosa Benth. Although A. omninigra is an oligolege of Clarkia, none of its pollen host plants were in bloom in the vicinity. Linsley suggests that the bees were foraging in the shade to minimize absorption of radiant heat through their black integument. He further suggests that the flies developed an early search image for these black bees foraging in patches of flowers in the shade and continued to prey on them while ignoring other brightly colored Osmia and other Andrena species foraging in sunny patches of the flowers.
FLORAL RECORDS. Andrena omninigra is an oligolege of Clarkia spp. (MacSwain, et al. 1973). It has been collected from flowers of the plants listed below.
Brassica sp., Calochortus venustus, Cercocarpus betuloides (as douglasii), Chamaebatia foliolosa, Clarkia sp., C. amoena huntiana, C. biloba, C. cylindrica, C. dudleyana, C. mildrediae, C. purpurea, C. quadravulnera, C. rhomboidea, C. speciosa, C. s. polyantha, C. unguiculata, C. williamsoni, C. xantiana, Cryptantha sp., C. flaccida, Eriodictyon californicum, Eriogonum sp. Gilia capitata, Rhamnus californica, Sidalcea malvaeflora.
Andrena omninigra Viereck, 1917, Trans. American Ent. Soc., 43: 385-386; Linsley, 1938, Proc. California Acad. Sci., Ser. 4, 23: 265, 277.
Andrena grundeli Linsley, 1938, Proc. California Acad. Sci., Ser. 4, 23: 265, 267, 274-275.
Andrena (Melandrena) grundeli grundeli: Linsley and MacSwain, 1955, Pan-Pacific Ent., 31: 164, 165; Linsley, MacSwain and Smith, 1955, Pan-Pacific Ent., 31: 176; Linsley and MacSwain, 1955, Pan-Pacific Ent. 31: 166; Linsley and MacSwain, 1961, Pan-Pacific Ent., 37: 127 (synonymy).
Andrena (Melandrena) omninigra: Lanham, 1949, Univ. California Publ. Ent., 8: 221.
Andrena (Onagrandrena) omninigra: Linsley and MacSwain, 1956, Pan-Pacific Ent., 32: 112, Linsley and MacSwain, 1961, Pan-Pacific Ent., 37: 127, 128 (synonymy); Linsley, 1972, Pan-Pacific Ent., 48: 94-96; MacSwain, Raven and Thorp. 1973, Univ. California Publ. Ent., 70: 14, 41, 43, Tables 1, 2, 5-11. 13. 18. (synonymy).
Andrena (Onagrandrena) omninigra clarkiae Linsley and MacSwain, 1961, Pan-Pacific Ent., 37: 127-128; MacSwain, Raven and Thorp, 1973, Univ. California Publ. Ent, 70: 15-16. New synonymy.
Updated: 2021-05-13 11:46:42 gmt