Reprinted with permission of the American Entomological Society from:
LaBerge, W. E. 1971b. A revision of the bees of the genus Andrena of the Western Hemisphere. Part IV. Scrapteropsis, Xiphandrena, and Rhaphandrena. Transactions of the American Entomological Society 97: 441-520.
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This small species is immediately recognizable by usually having two submarginal cells and by the relatively well-formed pronotal humeral angle and dorsoventral ridge in both sexes. Except for these two obvious characteristics, biareola is remarkably similar to stipator in color and sculpture, especially in the female sex. The male of biareola differs from that of stipator by the longer mandibles, the broader genal area and the less punctate terga.
FEMALE. MEASUREMENTS AND RATIOS. — N = 20; length, 9-10 mm; width, 2.5-3.0 mm; wing length, M = 3.24 ± 0.107 mm; FL/FW, M = 0.92 ± 0.003; FOVL/FOVW, M = 3.05 ± 0.042.
INTEGUMENTAL COLOR. — Black except as follows: mandible and apical half or more rufescent; flagellar segments 3-10 dark brown below; wing membranes hyaline, colorless or almost so, veins dark brown to reddish-brown; distitarsi dark rufescent, tibial spurs testaceous.
STRUCTURE. — Antennae as in stipator. Eyes each three and three-fourths times as long as broad, inner margins parallel. Malar space, mandible and galea as in imitatrix. Maxillary palpus as in imitatrix but segmental ratio about 1.0: 1.0: 0.8: 0.7: 0.5: 0.5. Labial palpus as in imitatrix but ratio about 1.0: 0.6: 0.4: 0.5. Labral process and labrum as in stipator but apical part of process often slightly narrower. Clypeus as in stipator but median impunctate line weak (holotype) or incomplete. Supraclypeal area as in stipator. Genal area in profile distinctly broader than eye (about as 5 or 6:4); laterally with rather coarse punctures, shiny except posteriorly shagreened, without rugulae or these weak; ventrally with coarse rugae converging towards midline and scattered interrugal punctures. Vertex and face above antennal fossae as in stipator but facial rugae usually more regularly longitudinal. Facial fovea as in stipator.
Pronotum with distinct humeral angle and sharp dorsoventral ridge extending down to the oblique pronotal suture. Wings with two submarginal cells (one specimen with three cells); pterostigma only slightly broader than from inner margin prestigma to wing margin. Thoracic sculpturing as in stipator. Legs as in stipator; middle femur broad.
Metasomal tergum 1 sculptured as in stipator but basal area punctures not as crowded medially. Tergum 2 as in stipator but apical area punctures separated mostly by half to one puncture width. Terga 3 and 4 as in stipator but punctures progressively sparser and apical area of tergum 4 almost impunctate. Pygidial plate and sterna as in stipator.
VESTITURE. — Generally white with same exceptions as in stipator; form and distribution of hairs as in stipator.
MALE. MEASUREMENTS AND RATIOS. — N = 6; length, 8-9 mm; width, 1.5-2.5 mm; wing length, M = 3.08 ± 0.266 mm; FL/FW, M = 0.93 ± 0.014; FS1/FS2, M = 1.57 ± 0.050.
INTEGUMENTAL COLOR. — Black except as follows: mandible with apical third rufescent; flagellar segments 2-11 dark brown below; wing membranes hyaline, veins dark reddish-brown; tergal apices rufescent; distitarsi rufescent; tibial spurs testaceous.
STRUCTURE. — Antennae short; scape length equal to about first two and one-half flagellar segments; flagellar segment 1 much longer than segment 2 and only slightly longer than 3; segment 2 quadrate, segments 3-11 longer than broad. Eyes as in imitatrix. Mandible decussate. Galea and malar space as in imitatrix. Maxillary palpus as in female but segmental ratio about 0.9: 1.0: 0.9: 0.7: 0.5: 0.5. Labial palpus as in female but ratio about 1.0; 0.6: 0.4: 0.6. Labral process as in stipator but slightly narrower apically. Clypeus as in female but usually lacking impunctate median line (allotype). Genal area broad, in profile equal to about one and one-half times width of eye or slightly more; laterally with small scattered punctures separated mostly by one or slightly more puncture width and dense shagreening dulling surface; ventrally with distinct longitudinal rugae converging slightly towards mandibles Vertex and face above antennae as in stipator.
Pronotum with distinct humeral angle and dorsoventral ridge as in female. Thoracic sculpture as in stipator but mesoscutal punctures somewhat sparser (but obscured by the dense tessellation) and mesepisternal punctures smaller. Wing venation as in female. Legs as in stipator.
Metasomal tergum 1 with basal area punctures small, obscure, separated by two to five puncture widths; apical area impunctate except scattered minute punctures in narrow band at base; surface shiny, shagreening present but delicate. Terga 2-5 similar to tergum 1 but basal area punctures more crowded, separated mostly by one to two punctures on tergum 2 and progressively sparser posteriorly; surfaces lightly shagreened. Vestigial pygidial plate absent. Sterna as in stipator.
Terminalia as in /4. stipator except the seventh sternal plate more broadly notched and somewhat thicker apically and eighth sternum with apical hyaline tip broader, broadly rounded at tip.
VESTITURE. — Generally white but abundant black hairs on vertex and on face along inner margins compound eyes. Distributed as in stipator but clypeal hairs denser and metasomal terga 1 and 2 with longer hairs in basal areas.
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