Reprinted with permission of the American Entomological Society from:
LaBerge, W. E. 1985. A revision of the bees of the genus Andrena of the Western Hemisphere. Part XI. Minor subgenera and subgeneric key. Transactions of the American Entomological Society 111: 440-567.
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Linsley (1938) first correctly associated males and females of A. caliginosa. This species can be readily recognized in the male by the long, finger-like process on the inner margin near the apex of the anterior trochanter and the pale yellow clypeus. The female is an all-black species with a relatively short malar space (as in berberidis ), short narrow facial foveae, weakly differentiated propodeal corbicula, and dense tibial scopa. The glossa of caliginosa is unique in being not at all pointed but rounded apically and about as long from the paraglossae to the tip as broad. The facial sculpturing and weak pronotal humeral angle are reminiscent of those of berberidis.
FEMALE. MEASUREMENTS AND RATIOS: N = 20; length 9-11 mm; width, 2.5-3.5 mm; wing length, M = 3.97 ± 0.196 mm; FL/FW, M = 1.01 ± 0.026; FOVL/FOVW, M = 3.14 ± 0.044.
INTEGUMENTAL COLOR. — Black except as follows: mandible with apical third or less rufescent; flagellar segments 2-10 dark brown below; tegula dark; wing membranes hyaline, slightly infumate, yellowish-brown, veins dark brown to black; terga with apical areas with dark rufescent reflections; sternal bases with rufescent reflections; tibial spurs piceous.
STRUCTURE. — Antennal scape length equals first two and one-half flagellar segments; flagellar segment 1 as long as next two and three-fourths segments; segment 2 slightly shorter than 3, 3 slightly shorter than 4, segment 3 about as long as broad. Eyes each almost three and one-third times as long as broad, inner margins parallel. Malar space short, minimum length equals about one-fourth basal mandibular width. Glossa short, broad, tip rounded, from paraglossae to apex about as long as broad. Galea as in berberidis, but dulled by fine shagreening, shorter than median clypeal length. Maxillary palpus as in berberidis, but segmental ratio about 1.0:1.0:0.8:0.8:0.6:0.8. Labial palpus as in berberidis, but ratio about 1.0:0.5:0.4:0.5. Labral process trapezoidal, bidentate, flat basally; labrum apical to process as long as process or longer, with median crista, flat or slightly convex laterally. Clypeus protuberant, narrowed apically, with coarse round punctures separated mostly by half a puncture width or slightly more, impunctate midline absent or extremely weak; surface shiny, weakly shagreened except near base. Supraclypeal area small, triangular, dulled by extremely small punctures and irregular shagreening. Face above antennal fossae with coarse rugulae diverging toward ocelli except laterally paralleling facial foveae, interrugal spaces with punctures and shagreening dulling surface. Facial fovea small, not extending below a line at lower margins antennal fossae, above separated from lateral ocellus by three-fourths to one ocellar diameter. Vertex short, above lateral ocellus usually equal to slightly less than one ocellar diameter; surface opaque, tessellate. Genal area in profile equal to slightly more than width of eye, with minute sparse punctures and reticular shagreening moderately dulling surface.
Pronotum with humeral angle absent or extremely weak, dorsoventral ridge weak;
surface finely shagreened. Mesoscutum with distinct round punctures separated by one to two puncture widths posteromedially, mostly by less than one puncture width anteriorly and laterally; surface dulled by reticular shagreening. Scutellum similar but punctures separated by half to one puncture width, shagreening often finer, surface moderately shiny. Metanotum dull, finely tessellate, obscurely punctate. Propodeum with dorsal enclosure tessellate; dorsal surface short; dorsolateral and posterior surfaces finely tessellate with obscure shallow punctures; lateral surface finely tessellate. Mesepisternum reticularly shagreened with small shallow punctures separated by half to one puncture width.
Metasomal tergum 1 with minute sparse punctures both in apical and basal areas, punctures separated by two to four or more puncture widths, surface dulled by reticular shagreening. Terga 2-4 similar to 1 but surfaces slightly shinier, shagreening weaker. Pygidial plate V-shaped, apex broadly rounded, internal raised triangle present, narrow. Sterna as in berberidis, apical areas short.
VESTITURE. — Entirely dark brown to black; tibial scopal hairs usually slightly paler brown than hairs elsewhere. Tibial scopal hairs long, simple; trochanteral flocculus complete; propodeal corbiculum with long plumose hairs above curling downward and long plumose internal hairs but no hairs much differentiated from long plumose thoracic hairs. Vestiture composed of relatively sparse, long, often weakly plumose hairs; without condensed apical tergal fasciae.
MALE. MEASUREMENTS AND RATIOS. — N = 4; length, 9-10 mm; width, 2.5-3.0 mm; wing length, 3.48-3.98 mm; FL/FW, 0.95-1.01; FS1/FS2, 2.20-2.44.
INTEGUMENTAL COLOR. — As in female except as follows: clypeus pale yellow except narrow apical margin, lateral angles, narrow posterior area and spots below tentorial pits.
STRUCTURE. — Antennal scape length equals first two and one-fourth flagellar segments; flagellar segment 1 about as long as segments 2 plus 3 and more than twice as long as segment 2, which is about as long as broad. Malar space about one-third as long as base of mandible, shiny. Glossa and galea as in female. Maxillary palpus as in female, but segmental ratio about 0.9:1.0:0.9:0.9:0.8:0.6. Labial palpus as in female, but ratio about 1.0:0.7:0.7:0.6. Labral process broad, short, flat, weakly bidentate, without basal transverse sulcus; labrum apical to process as long as process, flat, shiny, without distinct cristae. Clypeus moderately protuberant, with coarse round punctures irregularly separated by half to one puncture width or more, surface shiny, shagreening absent or extremely light. Supraclypeal area, face above antenna! fossae, and vertex as in female. Genal area as in female, but with weak rounded posterior angle, not as broad as in berberidis.
Thoracic form and sculpturing as in female except as follows: scutellum shiny, unshagreened, mesoscutum moderately shiny posteromedially, lightly shagreened; fore trochanter with a finger-like projection on inner surface near apex, adjacent surface of femur often angulate or with a short projection.
Metasomal terga 1-5 sculptured as in female terga 1-4. Tergum 7 without pseudopygidial area or this area extremely narrow, hairy. Sterna 2-5 as in berberidis but duller. Sternum 6 with apical margin weakly reflexed, narrowly emarginate. Terminalia as in berberidis, but dorsal lobe gonocoxite slightly swollen near base and then tapered, sternum 8 distinctly emarginate apically (Figs. 17-21).
VESTITURE. — Black except as follows: vertex, dorsum of thorax, and terga 1 and 2 with some long pale hairs mixed with dark (one specimen with few pale hairs on thorax); one specimen with coxa, trochanters, and bases of femora with pale hairs. Sterna 2-5 with subapical fimbriae of long, pale brown to cinereous hairs.