Reprinted by permission of the Regents of the University of California from:
Donovan, B. J. 1977. A revision of North American bees of the subgenus Cnemidandrena (Hymenoptera: Andrenidae). University of California Publications in Entomology: 1-107.
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Males are unknown for this species, but the females would seem to fit better within the Nubecula group than elsewhere. The vestiture is white, the wings hyaline, and metasomal tergum 1 has a thin apical fascia. The species has been taken from only a few locations near San Francisco in California, and is therefore allopatric to both A. bocensis and A canadensis, the two species with which it would seem to be mostly closely related. Its large size and thin apical fascia on tergum 1 distinguish it from other species within the Nubecula group.
FEMALE. MEASUREMENTS AND RATIOS. — N = 10; length, 8.9-9.7 mm; width, 2.8-3.2 mm; wing length, M = 3.12 ± 0.068 mm; FL/FW, M = 0.93 ± 0.077; FOVL/FOVW, M = 2.94 ± 0.247.
INTEGUMENTAL COLOR. — Black except as follows: antenna brown ventrally beyond second flagellar segment; mandible with more than apical half red; tibial spurs yellow; medio- and distitarsi and basal half of tarsal claws yellow, apical half of tarsal claws red; tegula, wing veins, and pterostigma dark brown, wing membrane hyaline except for very slight, apical darkening; metasomal terga and sterna with apical margin narrowly hyaline; pygidial plate red.
STRUCTURE. — Scape as long as flagellar segments 1 to 3 plus one-third of flagellar segment 4; flagellar segment 1 equal to flagellar segments 2 plus 3; flagellar segment 2 equal to flagellar segment 3. Eye slightly less than 4 times longer than wide, inner margin subparallel except for upper end somewhat incurved. Malar space 9 times wider than long. Mandible in repose extends for one-fourth its length beyond middle of labrum, notch of mandible tooth equidistant between middle of labrum and mandible apex. Galea moderately tessellate, dorsal surface wider than lateral surface. Maxillary palpus with half apical segment projecting beyond apex of galea, segmental ratio 1.1:1.2:0.9:O.9:0.7:1.1. Labial palpus with basal segment laterally flattened and curved, apical segment attached slightly subapically, segmental ratio 1.9:0.9:1.7:1.0. Labral process flattened except apical, lateral areas slightly recurved, more than twice as wide as long, apical emargination depth one-fourth length of labral process. Clypeus moderately protuberant, with very slightly more than half its length projecting below eyes, with large punctures separated by 1 diameter except more widely spaced on lower, median, flattened area; upper peripheral third shagreened, remainder shiny. Supraclypeal area with medium-sized, deep punctures separated by one-half diameter, with very weak shagreening, shiny. Genal area nearly 1.25 times wider than eye, with small to medium-sized punctures separated by one-half to 1 diameter, third nearest eye shiny, remainder shagreened. Vertex above lateral ocellus slightly wider than 1 ocellar diameter, with large, deep punctures separated by 1 diameter, punctures obscured by weak tessellation. Supra-antennal area with longitudinal rugulae and indistinct, interrugal punctures. Facial fovea 3 times longer than wide, slightly narrowed below, rounded above and below, reaching above to a line above median ocellus, reaching below to just below a line below antennal fossa.
Pronotum with humeral angle well developed, humeral ridge well developed below, broadly depressed medially where reached by pronotal suture; with small, scattered punctures dorsally, weakly shagreened throughout. Scutum with small to medium-sized punctures separated by 1 to 3 diameters; anterior half and small posterior area moderately tessellate, dorsal area smooth, shiny. Scutellum medioposteriorly with small punctures, remainder smooth, shiny. Metanotum with small, widely spaced punctures, moderately tessellate. Propodeal enclosure with narrow, anterior fringe of short, longitudinal rugulae, median, longitudinal area depressed, remainder moderately tessellate; dorsoposterior area with medium-sized punctures separated by 2 to 3 diameters; corbicular area with reticular shagreening. Mesepisternum with large punctures separated by 2 diameters, with reticular shagreening. Metepisternum with very small, sparse punctures dorsally, and very fine, reticular shagreening, nearly shiny. Mesobasitarsus expanded medially, 3 times longer than wide, equal in width to metabasitarsus. Metabasitarsus widest in basal fourth, slightly more than 4 times longer than wide, four-fifths width of metatibia. Metatibia cuneate, 4.3 times longer than wide. Wing with pterostigma 4 times longer than wide; vein 1st m-cu meets second submarginal cell one-fourth of distance from apex. Metasomal tergum 1 with medium-sized punctures separated by 2 diameters except punctures more widely spaced medially, whole area weakly tessellate; terga 2 to 4 with small to medium-sized punctures separated on discs by 3 or more diameters, on apical margins of discs by less than 2 diameters, with weak tessellation except depressed apical areas with reticular shagreening. Tergum 5 with large punctures separated by 2 or more diameters, with reticular shagreening. Pygidial plate rounded and slightly downturned apically, flat, with very small crowded punctures. Sternum 1 with small, median, V-shaped emargination, sterna 1 to 5 with medium-sized punctures separated by 2 diameters except punctures smaller basally and larger, more widely spaced on sternum 1; sternum 6 with medium-sized punctures apically, sternum 1 with very weak, reticular shagreening, sterna 2 to 6 with reticular shagreening.
VESTITURE. — White. Clypeus with sparse hairs in broad, median area; scutum naked on shiny, dorsal area, scutellum naked except for posterior and lateral edges, propodeal corbicula with scattered hairs in anterodorsal third, trochanteral floccus nearly perfect. Metatibial scopa with hairs of posterior face with very short branches on inner side.
Metasomal terga 1 to 4 with complete apical fasciae; fascia of tergum 1 with hairs nearly erect, not obscuring surfaces, fasciae of terga 2 to 4 with hairs appressed, obscuring about one-third of terga, discs of terga 2 to 4 with very short, sparse, erect hairs, tergum 5 obscured by long, recumbent hairs. Sternum 1 with sparse, long, erect hairs; sterna 1 to 5 with apical fringes of very short, appressed hairs, subapical fimbriae present in lateral thirds, fimbrial hairs barbed on inner sides; remainder of sternal areas with erect hairs, hairs becoming shorter anteriorly.
VARIATION. — All specimens are similar except for slight differences in overall size.