Reprinted with permission of the American Entomological Society from:
LaBerge, W. E. 1989. A revision of the bees of the genus Andrena of the Western Hemisphere. Part XIII. Subgenera Simandrena and Taeniandrena. Transactions of the American Entomological Society 115: 1-56.
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This small species from California and Oregon is similar to Andrena nasonii in having the fore wing with vein r short, but differs in the female by the narrower hind tibiae with relatively long scopal hairs, which are plumose along the anterior and posterior margins and simple only in a narrow median zone. The male can be recognized by the long first flagellar segment (longer than the second flagellar segment). Both sexes of subtrita have the galeae relatively shiny, with only weak shagreening and short vertices. This species seems to be intermediate in the form of the scopal hairs between species with short, simple hairs and those with long, highly plumose hairs.
FEMALE. MEASUREMENTS AND RATIOS. — N = 20; length, 7-8 mm; width, 1.5-2.5 mm; wing length, M = 2.70 ± 0.090 mm; FL/FW, M = 0.96 ± 0.006; FOVL/FOVW, M = 3.84 ± 0.071.
INTEGUMENTAL COLOR. — Black except as follows: mandible with apical half or more rufescent (rarely entirely rufescent); flagellum rufescent to reddish brown below; wing membranes hyaline, veins dark red to yellow, pterostigma usually pale; metasomal tergal ap-ical areas translucent, yellow toward base, colorless apically; tarsi dark reddish brown; tibial spurs testaceous.
STRUCTURE. — Antennal scape as long as first three and three-fourths flagellar segments; flagellar segment 1 longer than segments 2 and 3 together; segment 2 about as long as segment 3 and shorter than 4, broader than long. Eyes, malar space, and mandibles as in nasonii. Galeae as in nasonii but surface shiny to moderately shiny, shagreening fine and weak. Maxillary palpus as in nasonii but segmental ratio about as 1.0:1.0:0.7:0.6:0.6:0.8. Labial palpus as in nasonii but ratio about as 1.0:0.3:0.3:0.4. Labral process rounded apically, short (half as long as broad or shorter) with tip slightly upturned; labrum apical to process concave, dull, without cristae. Clypeus rounded, punctures often weak and obscured by dense tessellation, occasionally distinct in apical half and surface slightly shiny. Face above antennal fossae as in nasonii. Facial fovea as in nasonii but slightly narrower. Vertex shorter than lateral ocellus. Genal area as in nasonii.
Pronotum as in nasonii. Mesoscutum with small punctures separated mostly by two or three puncture widths or more, surface I usually dull, coarsely shagreened, occasionally shiny and smooth; | scutellum and metanotum similar. Propodeum with dorsal enclosure with fine irregular roughening especially basally, often with a single long median rugula, occasionally smooth, tessellate; dorsolateral surfaces roughened by coarse punctures and coarse tessellation. Fore wing with vein r long, usually four or five vein widths in length or longer.
Metasomal tergum 1 with basal area with extremely small and shallow, scarcely visible punctures to distinctly punctate with small punctures separated mostly by about one puncture width, surface usually dulled by fine shagreening, rarely moderately shiny; basal area usually impunctate, shagreened, specimens with basal area punctate have punctures in basal half of apical area. Terga 2-4 similar but punctures usually more evident in less punctate specimens and punctate specimens with punctures separated mostly by less than one puncture width. Pygidial plate V-shaped with narrowly rounded apex, internal triangular raised area weak. Sterna 2-5 as in nasonii.
VESTITURE. — White to dark ochraceous. Tibial scopal hairs usually pale, brown on and near basitibial plate; long, distinctly and loosely plumose throughout. Propodeal corbiculum complete. Trochanteral flocculus complete, small. Metasomal terga 2-4 with distinct, usually thick, pale, apical fasciae, that on tergum 2 usually interrupted, rarely so on tergum 3.
MALE. MEASUREMENTS AND RATIOS. — N = 20; length, 6-8 mm; width, 1-2 mm; wing length, M = 2.65 ± 0.164 mm; FL/FW, M = 0.91 ± 0.019; FS1/FS2, M = 1.58 ± 0.049.
INTEGUMENTAL COLOR. — As in female except as follows: mandible with apical third or less rufescent, flagellum dark brown to reddish brown below, terga with apical areas usually narrowly hyaline apically.
STRUCTURE. — Antennal scape as long as first two and one-third to two and one-half flagellar segments; flagellar segment distinctly longer than segment 2; segment 2 shorter than segment 3 and about as long as broad; median segments longer than broad. Eyes, malar space, and galea as in female. Maxillary palpus as in female but segmental ratio about as 1.0:1.0:0.2:0.2:0.8:0.9. Labial palpus as in female but ratio about as 1.0:0.4:0.4:0.5. Labral process as in female but usually more triangular than rounded; labrum apical to process without cristae, dull. Clypeus usually dull, opaque, finely tessellate with obscure punctures but often with minute distinct punctures and surface moderately shiny. Supraclypeal area, face above antennal fossae, and vertex as in female. Genal area in profile slightly broader than eye, dull, tessellate.
Pronotum as in female. Thoracic sculpturing as in female but propodeal dorsal enclosure usually more granular. Metasomal sculpturing as in female but terga 2-5 with basal areas with sparse puncture often evident but obscured by shagreening; sterna as in female; sternum 6 flat, shallowly emarginate apically. Terminalia as in Figures 37-41.
VESTITURE. — White to pale ochraceous except face above supraclypeal area or above antennal fossae and along inner margins eyes black. Clypeus with dense beard of long white pubescence usually obscuring surface; metasomal terga 2-5 with apical pale fasciae reduced to short lateral patches; sterna 2-5 without subapical fimbriae.
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