Reprinted by permission of the Regents of the University of California from:
Thorp, R. W. 1969. Systematics and ecology of bees of the subgenus Diandrena (Hymenoptera: Andrenidae). University of California Publications in Entomology 52: 1-146.
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This species is most closely related to A. evoluta from which it is distinguished by the finer sculpturing of the propodeal enclosure, the paler color of the anal fimbria, and the more elevated and more sharply denned dorsolateral angles of the pronotum. The two species are allopatric and exhibit no tendency toward intergradation even in southern Oregon where their populations are in: closest proximity. The treatment of these two taxa as full species is somewhat arbitrary. It may later turn out that they represent subspecies of one widespread polymorphic species.
Andrena chalybioides females from the foothills of the Sierra Nevada and the Transverse and Peninsular ranges of southern California exhibit increasing percentages of white hairs centrally on the face in population transects from north to south. In populations in the coastal mountains from San Luis Obispo County, California, north to Washington, females have uniformly black facial pubescence.
FEMALE. — Integument blue-green; antenna basally and above apically dark blackish-brown, reddish-brown below on apical 6 to 7 flagellar segments; forewing with stigma dark reddish-brown; clypeus with subapical, transverse dark band with violaceous reflections; pubescence pile, whitish on occiput, lower gena, metanotum, and lower pleura, black with violaceous tints on face, upper gena, and upper pleura, pale violaceous-gray on anal fimbria, outer surface of tibial scopa white anteriorly, violaceous-gray posteriorly, mesothoracic dorsum with long white and short black hairs intermixed; facial fovea with sheen black, tomentum brown above, white below. Head tessellate, densely punctate; clypeus, latero- and supraclypeal areas moderately coarsely, closely punctate with tessellate interspaces, punctures separated by less than one diameter; facial fovea extending from summit of eye to bottom of antennal base; eye slightly arcuate medially; antenna with segments 1 to 3 of flagellum as 15: 6: 6; labrum with process flat, bifid apically (fig. 21); subgenal coronet long, well developed; gena finely punctate with dull tessellate interspaces, punctures becoming coarser ventrally, separated by 2 to 3 diameters; pubescence of clypeus moderately long, sparse, suberect. Mesosoma finely, moderately closely punctate with dull, tessellate interspaces; pronotum tessellate, finely punctate, dorsolateral angle right-angled, not elevated, somewhat produced anteriorly with distinct lateral fold; mesoscutum with punctures moderately close, separated by 1 to 2 diameters, with finely granular, dull interspaces, notaulus short, distinct; scutellum with punctures larger, coarser, separated by one diameter or less, with finely granular, dull interspaces; metanotum rugose-punctate with punctures separated by less than one diameter, often confluent; propodeum rugose-punctate, enclosure irregularly rugulose basally, finely, transversely striate apically; episternum 2 rugose-punctate anteriorly, finely vertically striate posteriorly; wing lightly infuscated, submarginals 1: 2 (35: 47), stigma : rest of marginal cell (9: 28), hind wing with jugal lobe narrow, and without incision between it and vannal, reaching beyond level of cu-v (fig. 88); posterior trochanter with long, curved, white, perfect floccus; tibial scopa with long, moderately dense hairs, those of posterior three-fourths of outer surface branched, those on anterior fourth simple, posterior hairs of scopa nearly twice as long as width of tibia at apex; pubescence of mesoscutum of two lengths, short blackish and long whitish intermixed, hairs of ventral pleura long. Metasoma moderate shiny, finely, sparsely punctate with finely tessellate-granular interspaces, punctures separated by 1 to 3 diameters; pubescence of first tergum one and one-half times as long as that of tergum 2. Length 8.5 to 10.5 mm, forewing 7 to 8 mm.
MALE. — Integument greenish-blue; antenna uniformly dark brownish-black, clypeus with subapical margin dark and with violaceous reflections, forewing with stigma deep reddish-brown; pubescence pale, white except surrounding eye, on face, and gena black. Head tessellate, densely punctate, clypeus, latero- and supraclypeal areas coarsely, closely punctate with shiny finely tessellate interspaces, punctures separated by less than one diameter; parocular depression short, broad; eyes slightly convergent below; antenna with segments 1 to 3 of flagellum as 16:7:9, labrum with process bifid (fig. 22); mandibles long, decussate; gena finely punctate above with shiny, tessellate interspaces, below more coarsely punctate-tessellate; pubescence of clypeus moderately long, moderately dense, suberect. Mesosoma moderately closely, finely punctate with dull tessellate-granular interspaces; pronotum sparsely punctate, transversely tessellate, dorsolateral angle right-angled, not elevated, somewhat produced anteriorly with distinct lateral fold; mesoscutum with punctures separated by 1 to 2 diameters with dull granular interspaces; notaulus short, distinct; scutellum with punctures separated by about one diameter; metanotum rugose-punctate, punctures contiguous or occasionally confluent; propodeum rugose-punctate enclosure irregularly rugulose basally with fine transverse striae apically; episternum. 2 coarsely tessellate-punctate anteriorly, finely, vertically striate posteriorly; wing lightly infuscated, submarginals 1:2 (29:34), stigma : rest of marginal cell (14:21), hind wing with jugal lobe narrow and without incision between it and vannal, reaching beyond level of cu-v; pubescence of thoracic dorsum moderately long. Metasoma moderately shiny, finely punctate with granular interspaces, punctures separated by 2 to 4 diameters; pubescence pale, long erect on tergum 1, half as long erect on tergum 2, short suberect on terga 3 to 5. Length 7 to 9 mm, forewing 6 to 7 mm.