Reprinted with permission of the American Entomological Society from:
Ribble, D. W. 1974. A revision of the bees of the genus Andrena of the Western Hemisphere. Subgenus Scaphandrena. Transactions of the American Entomological Society 100: 101-189.
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This small species from southern Utah is very similar to Andrena nigerrima, although slightly larger in size. The female of nigricula differs from that of nigerrima by its broader facial fovea, shorter vertex, shinier galea, shinier thoracic dorsum and brown hairs on terga 5 and 6. The male of nigricula can be distinguished from that of nigerrima by its shinier galea, shorter vertex and shinier thoracic dorsum. With more material perhaps this form will be found to be only a well-marked geographic race of nigerrima, but the characters by which it differs from nigerrima warrant specific recognition.
FEMALE. MEASUREMENTS AND RATIOS. — N = 19; length, 10-12 mm; width 3-4 mm; wing length, M = 4.37 ± 0.173 mm; FL/FW, M = 1.11 ± 0.006; FOVL/FOVW, M = 2.88 ± 0.034.
INTEGUMENTAL COLOR. — Black except as follows: mandible with apical half rufescent; flagellar segments 3-10 dark reddish-brown below; wing membranes slightly infumate, brownish, veins brown to reddish-brown; terga and sterna with slightly rufescent reflections; tarsi and tibial spurs dark brown to black.
STRUCTURE. — Antenna as in nigerrima. Eyes each about three and one-half times as long as broad, inner margins converging extremely slightly toward mandibles. Mandible as in nigerrima. Galea as in nigerrima but shinier, shagreening absent or extremely weak. Maxillary palpus as in nigerrima but segmental ratio about as 1.0:1.0:0.9:0.8:0.6:0.6. Labial palpus as in nigerrima but ratio about as 1.0:0.8:0.6:0.6. Labral process as in nigerrima but apex slightly narrower; labrum below process with distinct median crista. Clypeus sculptured as in nigerrima but punctures slightly larger and separated mostly by half a puncture width or less, surfaces shiny. Supraclypeal area and face above antennal fossae as in nigerrima. Facial fovea as in nigerrima but slightly broader, above separated from lateral ocellus by half an ocellar diameter or slightly more. Vertex as in nigerrima but shorter, above lateral ocellus equals slightly more than half an ocellar diameter. Genal area as in nigerrima.
Thoracic form and sculpturing as in nigerrima except as follows: mesoscutum shiny except anterior third, reticular shagreening absent or extremely fine posteromedially; scutellum shiny, unshagreened, punctures sparser in posterior half; mesepisternal punctures more distinct, small, separated by half a puncture width or slightly more. Wing venation, tibial spurs and tarsal claws as in nigerrima.
Metasomal terga 1-4 shiny, punctured as in nigerrima but punctures slightly sparser; tergum 1 with basal area punctures separated by two to four or more puncture widths; tergum 2 with basal area punctures separated by one to two or more puncture widths. Pygidial plate broad, about as broad at extreme base as long, with rounded apex, lacking raised triangular area. Sterna as in nigerrima.
VESTITURE. — Entirely black to dark brown as nigerrima but terga 5 and 6 usually with long hairs brown. Distribution and form of hairs as in nigerrima but stipes with longer, more plumose hairs and propodeal corbicula with dorsal fringe of long plumose hairs.
MALE. . MEASUREMENTS AND RATIOS. — N = 5; length, 10-11 mm; width about 2.5 mm; wing length, M = 4.26 ± 0.391 mm; FL/FW, M = 1.23 ± 0.026; FS1/FS2, M = 1.99 ± 0.034.
INTEGUMENTAL COLOR. — Black with same exceptions as in female but clypeus pale yellow.
STRUCTURE. — Antenna as in nigerrima. Eyes each broad, slightly less than three times as long as broad, inner margins converging toward mandibles. mandible and galea as in female. Maxillary palpus as in female but segmental ratio about as 1.0:1.0:0.9:0.9:0.7:0.7. Labial palpus as in female but ratio about as 1.0:0.6:0.6:0.6. Labral process and labrum, clypeus, supraclypeal area and face above antennal fossae as in nigerrima. Vertex as in nigerrima but shorter, above lateral ocellus equal to slightly more than half an ocellar diameter. Genal area as in nigerrima.
Thoracic form and sculpturing as in nigerrima but mesoscutum and scutellum shinier as in female and mesepisternal punctures more distinct, separated largely by half a puncture width. Wing venation, tibial spurs and tarsal claws as in nigerrima.
Metasomal terga shiny, sculptured as in nigerrima but punctures sparser as in female. Sterna 2-5 as in nigerrima. Sternum 6 flat, rather deeply emarginate apically.
Terminalia (Figs. 6-10) similar to nigerrima but sternum 8 with neck expanded basally; penis valves narrower.
VESTITURE. — Entirely black or dark brown but last two terga with long brown hairs (paler than in nigerrima). Form and distribution of hairs as in nigerrima.
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