Reprinted by permission of the Regents of the University of California from:
Donovan, B. J. 1977. A revision of North American bees of the subgenus Cnemidandrena (Hymenoptera: Andrenidae). University of California Publications in Entomology: 1-107.
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Females of A. columbiana are readily distinguished from those of A. costillensis and A. pachucensis by the vestiture of metasomal terga 5 and 6 brown, and thus not concolorous with the white-yellow vestiture of the rest of the insect. Males are very difficult to separate from those of A. costillensis, and many males placed in A. columbiana may actually belong to A. costillensis. These two species appear to be very closely related.
FEMALE. MEASUREMENTS AND RATIOS. — N = 20; length, 7.8-9.7 mm; width, 2.4-3.4 mm; wing length, M = 3.64 ± 0.366 mm; FL/FW, M = 0.99 ± 0.079; FOVL/FOVW, M = 3.06 ± 0.175.
INTEGUMENTAL COLOR. — Black except as follows: antenna red-brown beneath beyond second flagellar segment; mandible with apical half red; tibial spurs light yellow; mediotarsi, distitarsi and basal half of tarsal claws red tinged with yellow; apical half of tarsal claws red; tegulae, wing veins dark brown; pterostigma yellow; wing membrane moderately darkened apically, lightly to moderately darkened throughout; metasomal terga with apical depressed area hyaline; pygidial plate dark red-black; sterna widely hyaline apically.
STRUCTURE. — Scape longer than flagellar segments 1 to 3; flagellar segment 1 longer than flagellar segments 2 plus 3; flagellar segment 2 very slightly shorter than flagellar segment 3. Eye less than 4 times longer than wide, with inner margin weakly diverging above except for upper end incurved. Malar space 9 times wider than long. Mandible in repose extends for one-fourth its length beyond middle of labrum with notch of mandible tooth equidistant between middle of labrum and mandible apex; ventrobasal angle and lamella well developed. Galea moderately tessellate, dorsal surface one-fourth wider than lateral surface. Maxillary palpus reaching a little beyond apex of galea; segmental ratio 0.8:1.2:0.8:0.8:0.7:0.7. Labial palpus with basal segment laterally compressed and curved; apical, subapical segment attached subapically, segmental ratio 1.4:0.7:0.7:0.7. Labral process with broad, lower, median bulge, emarginate area weakly reflexed, twice as wide as long, depth of apical emargination equal to one-fourth length of labral process. Clypeus weakly protuberant, extending below eyes for a little more than two-fifths its length, with narrow, median, longitudinal, impunctate area; large punctures laterally separated by less than one-half diameter, punctures much smaller near upper and lateral periphery; upper third moderately shagreened, remainder shiny. Supraclypeal area with crowded, medium-sized punctures and moderate shagreening. Genal area nearly twice as wide as eye, with small punctures separated by 1 diameter, narrow area near eye shiny, remainder shagreened, shagreening most dense posteriorly. Vertex above lateral ocellus equal to 1 ocellar diameter, with medium-sized, deep punctures separated by 1 diameter or more, with moderate tessellation. Supra-antennal area with longitudinal rugulae and close interrugal punctures. Facial fovea 3 times longer than wide, widest and rounded above; narrowing, more pointed below; reaching above to a line just above median ocellus; reaching below to a line equidistant between antennal fossa and clypeus.
Pronotum with humeral angle and ridge weakly to moderately developed; humeral ridge narrowly depressed where crossed by pronotal suture, with indistinct, scattered punctures above, whole area moderately shagreened. Scutum with strong tessellation obscuring indistinct punctures, dull; median mesoscutal line very well developed. Scutellum with posterior half with medium-sized punctures nearly obscured posteriorly by moderate tessellation; tessellation decreasing anteriorly, anterior third with few, scattered punctures, nearly smooth, shiny. Metanotum with roughened, moderate tessellation, punctures indistinct. Propodeal enclosure with very narrow, anterior median area of weak rugulae, moderately tessellate throughout with a broad, median, longitudinal depression; dorsoposterior area with medium-sized punctures separated by 1.5 diameters, moderately tessellate; lateral corbicular area with medium-sized, widely spaced punctures in anterodorsal third, with weak tessellation dorsally becoming reticular shagreening ventrally. Mesepisternum with large punctures irregularly spaced, moderately tessellate. Metepisternum with light, reticular shagreening, nearly shiny. Mesobasitarsus widest medially, 2.5 times longer than wide, equal in width to metabasitarsus. Metabasitarsus widest medially in basal half, a little less than 3 times longer than wide, five-sixths width of metatibia. Metatibia widest apically, curved ventrally, more than 3 times longer than wide. Wing with pterostigma 4 times longer than wide; vein 1st m-cu meeting second submarginal cell a little less than one-third distance from apex of cell.
Metasomal terga 1 to 4 with disc with small punctures separated by 1 to 3 diameters but closer apically on discs, with weak tessellation; tergum 5 similar but punctures slightly larger, more prominent. Pygidial plate slightly recurved, very narrowly rounded apically, with lateral edges and broad, median area raised, basal half with small, crowded punctures, anterior half smooth, dull. Sternum 1 with small, apical, V-shaped, median emargination, sterna 1 to 6 with small to nearly medium-sized punctures, separated by 2 or more diameters in apical half but punctures absent or nearly so in basal half or more; punctures more prominent on sternum 1; sterna very lightly shagreened, shiny.
VESTITURE. — Light yellow except for metasomal terga 5 and 6 with hairs dark brown and some brownish hairs on sterna 5 and 6. Clypeus with longitudinal, median, impunctate area naked. Scutum medially with sparse, short hairs. Scutellum with nearly shiny area naked. Propodeal corbicula with scattered, long, erect hairs in anterodorsal third, outer hairs branched, inner hairs simple. Metasomal tergum 1 with apical fascia of nearly flat to nearly erect hairs not obscuring tergal surface; terga 2 to 4 with fasciae of recumbent hairs, fasciae obscuring one-third or more of terga; remainder of discs of terga 1 to 4 with erect hairs, longest on tergum 1, becoming shorter posteriorly. Tergum 5 with surface nearly obscured by posteriorly directed hairs. Sternum 1 with long, erect, scattered hairs, sterna 1 to 5 with well developed apical fringes of 1 row of very short, branched hairs, subapical fimbriae with long hairs laterally on sterna 2 to 5, shorter, scattered hairs on remaining punctured areas.
MALE. MEASUREMENTS AND RATIOS. — N = 20; length, 6.5-9.0 mm; width, 1.8-2.3 mm; wing length, M = 3.21 ± 0.148 mm; FL/FW, M = 0.95 ± 0.022; FS1/FS2, M = 1.39 ± 0.083.
INTEGUMENTAL COLOR. — Black except as follows: antenna red-brown ventrally beyond first flagellar segment; mandible with apical third red; mesosoma, metasomal terga, and sterna as in female with apex of disc with light red-yellow tinge.
STRUCTURE. — Scape equal to flagellar segments 1 plus 2 plus half of flagellar segment 3; flagellar segment 2 equal to flagellar segment 3. Eye slightly longer than 3 times width with inner margin moderately diverging above except for upper end slightly incurved. Malar space, mandible and galea as in female except mandible projecting a little further past middle of labrum, and without ventrobasal angle or lamella. Maxillary palpus with almost whole of apical segment projecting beyond apex of galea; segmental ratio 0.8:0.9:0.6:0.8:0.7:0.7. Labial palpus as in female except segmental ratio 1.2 :0.6:0.5:0.7. Labral process very strongly reflexed, length of reflexed area about half width of process ; depth of apical emargination half length of reflexed area. Clypeus nearly flat, extending below eyes for two-fifths its length, with large punctures separated by one-half diameter except more widely separated medioventrally; very narrow upper peripheral area lightly shagreened. Supraclypeal area with close, irregular, medium-sized punctures, moderately shagreened. Genal area less than twice as wide as eye, with irregularly spaced, small to medium-sized punctures; posterior half shagreened, anterior half shiny. Vertex and supra-antennal area except rugulae obscure near eye.
Pronotum with humeral angle and ridge well developed except humeral ridge broadly and shallowly depressed medially; pronotal suture reaching humeral ridge; area above pronotal suture to humeral angle and ridge with longitudinal rugulae, shiny, area below pronotal suture nearly shiny or shiny; pronotum dorsally with small, obscure punctures, area above humeral ridge moderately shagreened. Remainder of mesosoma as in female except as follows: scutellum with anterior half shiny; lateral area of pronotum with moderate tessellation obscuring widely spaced punctures in dorsal half.
Metasomal terga 1 to 5 with small punctures on disc, separated by 3 diameters, but closer apically on disc, with very weak tessellation; except tergum 5 with punctures larger, more prominent. Sternum 1 with small, apical, median, V-shaped emargination; sterna 1 to 6 with small punctures separated by 3 to 5 diameters or more; with reticular shagreening, nearly shiny. Sternum 7 (fig. 33) with basal apodemes of equal width throughout; inner posterior margin indented; apex weakly pointed with long hairs. Sternum 8 (fig. 34) with apex and neck region longer than basal region; neck narrow, apex weakly expanded, neck with abundant, long hairs. Gonoforceps (figs. 30 to 32) in dorsal and lateral views ridged longitudinally, rounded apically. Penis valves with rounded, lateral expansion, apex lobe-like, strongly bent downward, extending well below gonoforceps.
VESTITURE. — Light yellow throughout. Clypeus with moderately dense hairs. Scutum and scutellum with moderately dense, moderately long, erect hairs, except scutellum with hairs sparse on shiny, anterior area.
Metasomal terga 1 to 5 with apical fasciae nearly obscuring a little less than one-half terga, except tergum 1 with apical fascia poorly formed, not obscuring surface, hairs nearly erect; fasciae of terga 2 to 5 with hairs more recumbent; remainder of discs with hairs erect, longest on tergum 1, becoming shorter on more posterior terga. Sternum 1 with long, erect, sparse hairs, sterna 1 to 5 with poorly formed apical fringe, remainder of sterna 2 to 6 with long, erect hairs laterally, shorter, erect hairs more anteriorly.
VARIATION. — In most females the longitudinal, impunctate, median line on the clypeus is not as well defined as described. The facial fovea varies in width above. In both sexes the vestiture may range from quite yellow to nearly white, (except for the dark brown vestiture of metasomal terga 5 and 6 in females) but the vestiture of some individuals is more white than yellow.