Reprinted with permission of the American Entomological Society from:
Bouseman, J. K., LaBerge, W. E. 1978. A revision of the bees of the genus Andrena of the Western Hemisphere. Part IX. Subgenus Melandrena. Transactions of the American Entomological Society 104: 275-390.
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Andrena platyrhina seems to be a relatively primitive Melandrena related to A. hilaris. The female of platyrhina is similar to hilaris in the relatively distinct apical fasciae of terga 2-4 but differs in the shorter vertex, more pointed labrum, and the more sparsely punctate clypeus which is more or less flattened posteromedially. The male of platyrhina can be distinguished from that of hilaris by the long first flagellar segment relative to the second segment, by the pointed labrum, the shiny clypeus and the fasciate terga.
FEMALE. MEASUREMENTS AND RATIOS. — N = 20; length, 12-14 mm; width, 3.5-4.0 mm; wing length, M = 4.95 ± 0.113 mm; FL/FW, M = 1.02 ± 0.004; FOVL/FOVW, M = 2.82 0.037.
INTEGUMENTAL COLOR. — Black except as follows: mandible with apical third to half rufescent; flagellar segments below reddish-brown; tegula translucent, ferruginous; wing membrane hyaline, slightly infumate, yellowish, veins red to reddish-brown (subcosta dark); terga 1-4 with apical area hyaline, yellow apically to rufescent basally; sterna 2-5 with apical areas hyaline, yellow; distitarsi rufescent; basitarsi and often middle and hind tibiae dark rufescent; tibial spurs red to testaceous.
STRUCTURE. — Antennae as in vicina but flagellar segment 1 slightly longer than segments 2 plus 3. Eyes each about four times as long as broad, inner margins parallel. Malar space, mandible and galea as in vicina. Maxillary palpus as in vicina but segmental ratio about as 0.9:1.0:0.7:0.6:0.6:0.5. Labial palpus as in vicina but ratio about as 1.0:0.6:0.5:0.6. Labral process broad at base, abruptly narrowed to a small often weakly emarginate apex, basal depression with three or four transverse striae; labrum below process long, obtusely pointed, shiny, with several extremely weak cristae. Clypeus long, flattened mediobasally, with round. punctures separated irregularly by half to one or more puncture widths (largely by one width) with impunctate median line present, narrow basally, often expanded near apex; surface shiny, unshagreened; lateral angles and often along prostomial suture laterally impunctate. Supraclypeal area with small distinct punctures, surface shiny to moderately so, unshagreened or delicately so. Face above antennal fossae and facial fovea as in vicina. Vertex short, above lateral ocellus equal to about one and one-half ocellar diameters or very slightly more (about as 8:12 or 13); sculptured as in vicina. Genal area almost twice as wide as eye in profile, with small punctures crowded near eye, shiny in third near eye margin and dulled by reticular shagreening posteriorly.
Thoracic form and sculpturing as in vicina except as follows: mesoscutal posteromedial area and scutellum moderately shiny (shagreened) to shiny (shagreening weak or absent); propodeal dorsal enclosure weakly roughened only basally; propodeal dorsal and posterior surfaces tessellate and punctate but punctures not roughening surface. Wing venation as in vicina but second submarginal cell usually receiving vein 1st m-cu well beyond middle of cell. Tarsal claws and tibial spurs at in vicina.
Metasomal terga 1-4 with punctures as in hilaris but apical areas with punctures slightly more crowded; tergum 1 dulled by fine reticular shagreening basally, terga 2-4 more or less shiny, shagreening weak or absent. Pygidial plate V-shaped with narrow, rounded apex, internal raised triangular area not evident except near bast. Sterna sculptured as in vicina.
VESTITURE. — Pale ochraceous to ochraceous except as follows: facial foveal hairs white; terga 5 and 6 and inner surfaces hind tarsi pale yellow to golden. Form and distribution of hairs as in hilaris; terga 2-4 with relatively weak but distinct apical pale fasciae (interrupted medially on terga 2 and 3), basal area hairs short, erect; thoracic dorsum with hairs relatively sparse, erect, of moderate length; scopal hairs dense and relatively short.
MALE. MEASUREMENTS AND RATIOS. — N = 20; length, 10-12 mm; width, 2.$-)J| mm; wing length, M = 4,51 ± 0.164 mm; Fl./FW, M = 0.98 ± 0.005; FS1/FSI.M = 1.64 ± 0.027.
INTEGUMENTAL COLOR. — As in female but terga 1-6 with apical areas hyaline, colorless or yellowish apically and rufescent basally.
STRUCTURE. — Antennae of moderate length, reaching midscutellum or slightly longer in repose; scape length equals first two and three-fourths flagellar segments or slightly more; flagellar segment 1 equals one and one-half times segment 2 or longer (rarely slightly shorter) and longer than segment 3; segment 2 quadrate; segments 3-10 one and one-third times as long as broad or almost. Eyes each three and one-half times as long as broad or slightly longer, inner margins parallel. Mandible, malar space and galea as in female. Maxillary palpus as in vicina but segmental ratio about as 0.9:1.0:0.8:0.8:0.8:0.7. Labial palpus as in vicina but ratio about as 1.0:0.8:0.7:0.8. Labral process broad a base, narrow apically, apical margin emarginate, often with a few distinct punctures in apical area as in illini, base of process without striae or with one or two striae; labrum apical to process with apical margin obtusely pointed medially, shiny without cristae. Clypeus with large round punctures separated mostly by half to one puncture width or slightly more, median impunctate line often present at least apically; shiny, shagreening absent or extremely weak and only at extreme base; impunctate lateral angles. Supraclypeal area, face above antennal fossae, vertex and genal area as in female.
Thoracic form and sculpturing as in female except as follows: propodeal dorsal area outside of enclosure and posterior surface roughened by punctures and fine tessellation. Wing venation, tarsal claws and tibial spurs as in female.
Metasomal terga sculptured as in hilaris but tergum 1 with basal area moderately dulled by fine shagreening, terga 1-5 with apical areas shiny, terga 2-5 with basal areas shiny, delicately shagreened at bases. Tergum 7 with narrow shiny pygidial area. Sterna 2-5 as in vicina. Sternum 6 with apical margin shallowly emarginate apically.
Terminalia as in figures 109-113; note sternum 7 with deep, almost U-shaped emargination and sternum 8 with apex slightly broadened.
VESTITURE. — Generally pale ochraceous, often slightly darker ochraceous on vertex and thoracic dorsum and inner surfaces tarsi golden. Terga 2-4 with weak, broadly interrupted, apical pale fasciae. Sterna 2-5 with weak, narrow, pale, subapical fimbriae (incomplete laterally). Thoracic dorsum with hairs long, erect, sparse.
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