Reprinted with permission of the American Entomological Society from:
LaBerge, W. E. 1985. A revision of the bees of the genus Andrena of the Western Hemisphere. Part XI. Minor subgenera and subgeneric key. Transactions of the American Entomological Society 111: 440-567.
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This fair-sized bee from California can be distinguished from the only other known member of the subgenus by the broader galeae with concave outer margins and the trochanteral flocculus with several long plumose hairs near the apex. The male of nigroclypeata has the same broad galeae as the female, usually an entirely black clypeus, and a much shorter first flagellar segment, as described below.
FEMALE. MEASUREMENTS AND RATIOS. — N = 20; length, 10-13 mm; width, 3-4 mm; wing length, M = 4.47 ± 0.220 mm; FL/FW, M = 0.84 ± 0.003; FOVL/FOVW, M = 2.57 ± 0.118.
INTEGUMENTAL COLOR. — Black except as follows: mandible usually entirely dark rufescent; clypeus near clypeofrontal suture and adjacent face often deep rufescent; flagellum below deep reddish brown. Wing membranes slightly infumate, yellow; veins dark reddish brown; tibial spurs yellow.
STRUCTURE. — Antennal scape as long as first three and one-half flagellar segments; flagellar segment 1 as long as following two and one-fourth segments; segment 2 quadrate; median segments slightly longer than broad. Eyes each three and three-fourths times as long as broad, inner margins parallel to slightly converging toward vertex. Malar space as in macrocephala. Mandible as in macrocephala, but inner tooth small, often not much more than a slight subapical angle. Galea normal, broad, apical half with outer margin slightly convex; surface dull, reticularly shagreened. Maxillary palpus as in macrocephala, but segmental ratio about 1.0:1.0:0.9:0.7:0.6:0.6. Labial palpus as in macrocephala, but segmental ratio about 1.0:0.6:0.5:0.5. Labral process entire, apical margin rounded to extremely weakly emarginate, shiny; labrum below process without cristae, with strong, shiny, transverse sulcus. Clypeus with small punctures separated mostly by half to one puncture width, surface dull to moderately shiny, especially apicomedially, finely shagreened; without median impunctate zone. Supraclypeal area, face, vertex, facial foveae, and genal areas as in macrocephala.
Pronotum without dorsoventral ridge; without humeral angles. Thorax sculptured as in macrocephala. Pterostigma about as broad as from inner margin prestigma to wing margin; vein 1st m-cu meets second submarginal cell slightly beyond middle.
Metasomal terga 1-4 impunctate, tergum 5 with sparse minute punctures, surfaces dulled by fine reticular shagreening. Pygidial plate and sterna as in macrocephala.
VESTITURE. — Generally as in macrocephala in darkest specimens except dorsum of thorax never red. Pale specimens with hairs pale ochraceous to dark ochraceous except as follows: vertex and face below ocelli with abundant dark hairs; fore and middle tarsi and tibiae, hind tarsi, and basitibial plates dark brown; posterior tibiae with scopal hairs brown at least along posterior margin; at least terga 3 and 4 with short hairs brown; terga 5 and 6 with pale brown hairs. Usually hind tibiae with scopal hairs brown to pale brown even in darker specimens.
MALE. MEASUREMENTS AND RATIOS. — N = 20; length, 8-12 mm; width, 1.5-2.5 mm; wing length, M = 3.66 ± 0.194 mm; FL/FW, M = 0.79 ± 0.009; FS1/FS2, M = 1.27 ± 0.019.
INTEGUMENTAL COLOR. — As in female except as follows: mandible with apical third to half rufescent; clypeus with apical half to three-fourths yellow in about one-fourth of specimens, entirely black in remainder; terga with apical area translucent, yellow brown.
STRUCTURE. — Antennal scape slightly shorter than first three flagellar segments together; flagellar segment 1 longer than segment 2 and slightly longer than 3, all segments longer than broad. Eyes each about three times as long as broad, inner margins converging slightly towards vertex. Mandible simple or weakly bidentate, when closed surpassing midlabrum by about one-fifth mandibular length, female-like. Galeae and malar spaces as in female. Labral process rhomboidal and weakly emarginate to rounded, flat, shiny. Maxillary and labial palpi as in female. Clypeus with small round punctures separated by one to two puncture widths, surface shiny to moderately shiny, reticular shagreening weak and dense only near base, without median impunctate line. Supraclypeal area, face above antennal fossae, vertex, and genal area in profile as in macrocephala.
Pronotum without dorsoventral ridge or ridge only weakly expressed, without humeral angle, with several fine rugulae following posterior margin in area where humeral angle occurs in other Andrena. Thoracic sculpturing and wing venation as in female, but scutellum sometimes moderately shiny.
Terga and sterna as in female but shinier and tergal punctures more evident on terga 1-5, although sparse. Sternum 6 as in macrocephala. Terminalia as in figures 119-123. Note penis valves narrow and elongate; sternum 8 narrow and apex bidentate.
VESTITURE. — Generally ochraceous except as follows: vertex with brown hairs mixed with pale; pleurae with reddish-brown hairs in part; terga 2-5 with short sparse brown hairs; terga 6 and 7 with golden to ochraceous hairs. Hind basitibial plates and outer surfaces tarsi and tibiae usually with some brown hairs. Pale specimens entirely pale ochraceous except dorsum of terga 3-5.
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