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 species is related to A. sladeni. The female of chapmanae can be distinguished by the facial fovea extending below the antennae, the long scopal hairs, the dark hairs on the thoracic dorsum and the rather dark luster on the thoracic dorsum. The male of: chapmanae has a short clypeus, flagellar segment 2 shorter than segment 3, sternal fimbriae and different genitalia.
The descriptions below are based mainly on a female from Canebrake Creek and a male from Walker Pass, California.
FEMALE. — MEASUREMENTS AND RATIOS. — Length, 10.5 mm; width, 2.9 mm; wing length, 7.6 mm; FL/FW, 1.02; FOVL/FOVW, 3.71.
INTEGUMENTAL COLOR. — Color as in merriami but body with bright blue-black luster on most areas, wing veins blackish.
STRUCTURE. — Flagellar segment 1 much longer than segments 2 plus 3; antenna otherwise as in merriami. Eyes each about 3.7 times as long as broad, inner margins parallel. Mandible as in merriami. Galea as in merriami but longer, very shiny, with weak shagreening apically, absent basally. Stipes hairs straight. Labial palpus as in merriami but ratio about 1.0:0.6: 0.6:0.6. Maxillary palpus as in merriami but ratio about 1.0:1.0:0.8:1.0: 0.7:0.8. Labrum as in merriami but process larger and weakly emarginate at apex. Clypeus as in merriami but center very shiny, unshagreened. Supraclypeal area, face above antennal fossae, vertex and genal areas as in merriami. Facial fovea as in merriami but extending down to below level of lower margins antennal fossae.
Pronotum as in merriami but punctures moderate in size, shagreening fine. Mesoscutum as in merriami but shinier, finer shagreening becoming absent in center. Scutellum in center sculptured as center of mesoscutum. Propodeum with dorsal area triangular, rather smooth; dorsolateral and posterior surfaces as in merriami but shiny, shagreening less even and finer; lateral surfaces very shiny otherwise as in merriami. Mesepisternum as in merriami. Wings as in merriami but vein 1st m-cu meets second submarginal cell beyond center of cell. Legs as in merriami.
Metasomal terga 1-5 as in merriami but punctures a little closer and larger. Pygidial plate as in merriami. Sterna 2-5 with moderate-sized close punctures, surfaces shiny, shagreening weak to absent.
VESTITURE. — As in merriami but thoracic dorsum with rather short dark hairs, tibial scopal hairs long.
MALE. — MEASUREMENTS AND RATIOS. — Length, 9.6 mm; width, 2.5 mm; wing length, 6.9 mm; FL/FW, 1.06; FS1/FS2, 1.89.
INTEGUMENTAL COLOR. — Color as in female except body with bluer luster, clypeus cream-colored except apex and two small dark spots.
STRUCTURE. — Antennae, eyes mandible and stipes as in merriami. Galea as in female. Labial palpus as in female but ratio about 1.0:0.5:0.4:0.6. Maxillary palpus as in female but ratio about 0.7:1.0:0.7:0.7:0.6:0.6. Labrum and clypeus as in merriami. Supraclypeal area, face above antennal fossae and vertex as in female. Genal area as in female but very shiny with fine shagreening.
Pronotum, mesoscutum, scutellum as in female. Propodeum as in female except shagreening coarser, becoming rugulose on basal part of dorsal triangular area. Mesepisternum, wings and tarsal claws as in female. Hind tibia as in merriami.
Metasomal sculpturing as in female but pygidial plate absent, sterna 2-5 with punctures more scattered. Sternum 6 deeply notched at apex.
Terminalia as in figures 90-94; note the following: gonocoxite with dorsal lobes moderate in length, broadly rounded, apex moderate in width; penis valve wide, without dorsal lamellae, apex short, thick, broadly rounded in ventral view; sternum 7 with apex truncate and deeply notched; sternum 8 with apex broader than neck region, apex slightly emarginate.
VESTITURE. — As in merriami but legs and abdomen with mostly dark hairs.
VARIATION. — A few of the females from the Sierras have white hairs at the sides of the scutellum or on the metanotum and one female has the white hairs extending along the sides of the mesoscutum. A female from Woodfords is entirely dark and lacks the bluish luster. Sometimes the hairs on the male legs and abdomen are mostly amber rather than chocolate brown. The male vertex of the head is often higher than one ocellar diameter.
Updated: 2021-05-12 02:21:59 gmt