Reprinted with permission of the American Entomological Society from:
LaBerge, W. E. 1980. A revision of the bees of the genus Andrena of the Western Hemisphere. Part X. Subgenus Andrena. Transactions of the American Entomological Society 106: 395-526.
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This species is closely related to A. buckelli with which it shares the tall vertex and somewhat flattened clypeus; The female of mesoleuca differs from that of buckelli by having dark hairs on the mesoscutum, especially anteriorly and anteromedially, and having apical white fasciae on terga 2 and 3 at least medially; The male of mesoleuca is almost identical to that of buckelli or ofsaccata but the vertex is equal to more than one ocellar diameter and the mesoscutum has distinct dark brown hairs medially and often anteriorly; The female of mesoleuca is also very much like a few specimens of thaspii which are intermediate between the pale and dark forms; However, the mesoleuca female has a taller vertex and a slightly longer malar space and pale hairs of the thoracic dorsum tend to be cinereous to white rather than ochraceous.
FEMALE. MEASUREMENTS AND RATIOS. — N = 20; length, 11-12 mm; width, about 3.5 mm; wing length, M = 4.37 ± 0.133 mm; FL/FW, M = 0.98 ± 0.003; FOVL/ FOVW, M = 3.12 ± 0.043.
INTEGUMENTAL COLOR. — Black except as follows: mandible with apical third or more rufescent; flagellar segments 2-10 reddish-brown below, wing membranes slightly infumate, veins dark brown, pterostigma rufescent; distitarsi dark rufescent; tibial spurs dark brown.
STRUCTURE. — Antennae as in vicinoides; Eyes each about three and one-half times as long as broad or slightly longer, inner margins parallel; Mandible as in vicinoides but lacking inferior basal tooth or angle; Malar space moderately long, more than one-fourth times as long as broad but slightly less than one-third times as long as broad; Galea as in vicinoides but dull; Maxillary palpal segments as in frigida but segmental ratio about as 0.8:1.0:0.8:0.8:0.6:0.6; Labial palpus as in frigida but ratio about as 1.0:0.6:0.6:0.6; Labral process trapezoidal, deeply emarginate (bidentate), reflexed, with transverse basal depression; labrum apical to process convex, dull, with weak median crista; Clypeus flattened apicomedially, with small round punctures separated mostly by half a puncture width or less, without distinct longitudinal impunctate line; surface shiny to moderately dull, shagreened at least in basal third or less; Supraclypeal area, face above antennal fossae and facial fovea as in vicinoides; Vertex tall, as in buckelli; Genal area broad, in profile one and one-half times as broad as eye or broader; sculptured as in buckelli but usually narrow zone adjacent to eye with moderately crowded minute punctures; Thoracic form and sculpturing as in vicinoides; Wing venation typical of subgenus; second submarginal cell square or slightly narrower anteriorly than posteriorly; Metasomal tergum 1 dulled by reticular shagreening; basal area with minute punctures obscured by shagreening but separated by one or slightly more puncture widths when visible; Terga 2-4 with basal areas with small punctures separated mostly by half to one puncture width; surfaces dulled by dense fine shagreening; apical areas similar but punctures less abundant especially in median third; Pygidial plate and sterna as in vicinoides.
VESTITURE. — Generally black except as follows: face surrounding antennal fossae white; facial fovea with lower half occasionally pale brown to ochraceous; mesoscutum with narrow peripheral zone pale ochraceous, a few to several pale hairs along midline; scutellum pale peripherally; propodeal dorsal area and posterior surface with long pale hairs; pleura with pale hairs above near wing insertions; tergum 1 with hairs white; tergum 2 with hairs white except a few to several dark hairs at extreme sides, with white apical fascia; tergum 3 with apical area with dense white fascia (often incomplete at extreme sides), basal area often with several long white hairs mixed with the dark medially; Form of pollen-collecting hairs as in vicinoides and buckelli; dorsal thoracic hairs short; terga 2-5 with basal areas with dense erect hairs.
MALE. MEASUREMENTS AND RATIOS. — N = 4; length, about 10mm; width, about 2.5 mm; wing length, M = 3.65 ± 0.003; FL/FW, M = 0.93 ± 0.001; FS1/FS2, M = 0.89 ± 0.003.
INTEGUMENTAL COLOR. — As in female but wing membranes hyaline, tergal and sternal apical areas slightly translucent.
STRUCTURE. — Antenna as in vicinoides but flagellar segment 1 slightly shorter than segment 2; Eyes each about three and one-fourth times as long as broad, inner margins converging slightly towards vertex; Mandible as in buckelli; Malar space slightly longer than one-fourth as long as broad and less than one-third as long as broad, shiny; Maxillary and labial palpi as in female; Labral process as in female but more strongly reflexed and not showing basal transverse depression; labrum apical to process shiny, convex, without cristae; Clypeus flattened apicomedially, with round punctures separated by half a puncture width or slightly more except in small apicomedian area; surface shiny, unshagreened except in basal fourth or less; Supraclypeal area, face above antennal fossae and vertex as in female; Genal area broad, much as in vicinoides; Thoracic form and sculpturing as in vicinoides; Wing venation as in female; Tergal sculpturing as in female but surfaces slightly shinier, shagreening finer and basal area punctures smaller and sparser; Tergum 7 with extremely narrow, sharply pointed pygidial area; Sterna 2-5 sculptured as in vicinoides', sternum 6 with apical margin narrowly, sharply reflexed.
Terminalia as in figures 162-166; note penis valves with blunt tips.
VESTITURE. — Head black except hairs surrounding antennal fossae and occiput; Thoracic hairs white to cinereous except mesoscutum with dark hairs medially; scutellum often with dark hairs medially; pleura with lower parts usually with dark hairs; Metasomal hairs dark brown except tergum 1 with long pale hairs and tergum 2 with basal half of basal area or less with long pale hairs and apical area often with short lateral white fasciae; Leg hairs dark brown to black; Form of hair as in vicinoides.
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