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.
Please report text errors to: leah at discoverlife dot org.
Andrena scurra, a western bee, readily hybridizes with the eastern A. arabis and the southwestern A. capricornis. The hybrids occur in the Great Basin area of the western United States and in the Rocky Mountain area. These trihybrids are treated in a separate section later in this paper. The keys above and the tables in Ribble (1973) can be used to separate scurra from arabis and capricornis. See Ribble also for range maps.
The descriptions below are based mainly on a female from 30 miles east of Bend, Oregon and a male from Pullman, Washington.
FEMALE. — MEASUREMENTS AND RATIOS. — Length, 9.0 mm; width, 2.9 mm; wing length, 7.5 mm; FL/FW, 1.03; FOVL/FOVW, 5.00.
INTEGUMENTAL COLOR. — Black to dark brown except as follows: mandible with apical half rufescent; wing membranes amber, veins dark amber; tegulae dark amber; terga 1-5 with apical areas amber; apical half of hind tibia and hind tarsus light brown; tibial spurs amber.
STRUCTURE. — Antennal scape nearly as long as first four flagellar segments; flagellar segment 1 slightly longer than segments 2 plus 3; segment 2 about equal in length to 3, broader than long and shorter than 4; segments 4-9 quadrate. Eyes each about 4.1 times as long as broad, inner margins converging slightly towards mandibles. Mandible moderately long, at rest reaching nearly to far corner of labrum, with inner subapical tooth. Galea pointed, broad, surface moderately dulled by fine reticular shagreening. Stipes with many mostly straight hairs. Labial palpus with first segment flattened, long, curved, segmental ratio about as 1.0:0.5:0.4:0.4. Maxillary palpus surpassing galea by more than last two segments, segmental ratio about as 1.0:1.0:0.8:0.8:0.8:0.8. Labral process wide basally, apically greatly narrowed to a subquadrate, emarginate elevation; labrum below process flat, dull. Clypeus rounded from side to side, center with large punctures separated mostly by one puncture width, surface moderately dulled by fine reticular shagreening. Supraclypeal area dulled by minute punctures and shagreening. Face above antennal fossae with distinct longitudinal rugulae and fine shagreening, moderately shiny. Facial fovea narrow, separated from lateral ocellus by two ocellar diameters, extending down to about level of lower margins antennal fossae. Vertex above lateral ocellus normal, about as high as one ocellar diameter, moderately shiny. Genal area only slightly wider than eye in profile; surface moderately shiny with minute punctures and fine reticular shagreening.
Pronotum without humeral angles or carinae, with small close punctures, finely shagreened. Mesoscutum moderately shiny to dull, with medium-sized punctures separated mostly by one puncture width, surface with reticular shagreening, except center of mesoscutum very shiny, with sparse punctures, devoid of microsculpture. Scutellum in center very shiny, with sparse punctures, devoid of microsculpture. Propodeum with dorsal area triangular with basal rugulae; dorsolateral and posterior surfaces with medium-sized punctures and rather coarse reticular shagreening; lateral surfaces shiny, with few small piliferous punctures, fine even reticular shagreening. Mesepisternum moderately dulled by small to medium-sized punctures and reticular shagreening. Wings with pterostigma medium-sized, broader than from inner margin prestigma to wing margin; vein 1st m-cu meets second submarginal cell just beyond center of cell; second submarginal cell medium-sized, subquadrate, slightly narrowed anteriorly. Tarsal claws with large, inner, subapical tooth; hind tibia greatly widened apically, triangular.
Metasomal terga 1-4 with distinct apicolateral elevations, shiny, with minute close punctures, fine shagreening becoming more distinct basally, graduli hidden with abdomen in normal position. Tergum 5 with large punctures, reticular shagreened. Pygidial plate V-shaped with rounded apex: internally plate rather smooth and gradually elevated above margins. Sterna 2-5 with very close minute punctures, surfaces shiny, fine reticular shagreening.
VESTITURE. — Generally white with a yellowish tinge, abundant. Thoracic dorsum with hairs mostly of moderate length, erect, weakly plumose, moderately abundant, hiding about 50% of surface anteriorly, posteriorly hairs sparse; propodeal corbicula incomplete anteriorly with several long simple internal hairs; tibial scopal hairs simple, moderately abundant, hiding about 75% of surface, becoming short towards apex of tibia, hairs along anterior margin mostly curved posteriorly. Metasomal terga 2-4 with broad, apical white fasciae, thinner medially on tergum 3, incomplete medially on tergum 2; sterna 2-5 with subapical fimbriae.
MALE. — MEASUREMENTS AND RATIOS. — Length, 8.7 mm; width 2.3 mm; wing length. 7.0 mm; FL/FW, 1.00; FS1/FS2, 1.50.
INTEGUMENTAL COLOR. — Black to dark brown with same exceptions as in female but clypeus light yellow except apex and two small dark spots, middle and hind tarsus and apical third of hind tibia light yellow-brown.
STRUCTURE. — Antennae of moderate length, reaching metanotum in repose; scape length about equal to first two and two-thirds flagellar segments; flagellar segment 1 nearly as long as segments 2 plus half of 3, segment 2 shorter than 3 and about as broad as long, segments 3-11 longer than broad. Eyes each about three times as long as broad, inner margins distinctly converging towards mandibles. Mandible and galea as in female. Stipes weakly setose. Labial palpus as in female but ratio about 1.0:0.3:0.4:0.8. Maxillary palpus as in female but ratio about 1.0:0.8:0.7:0.7:0.4:0.7. Labral process small, square, deeply notched at apex, elevated, labrum apical to process as in female. Clypeus as in female but shagreening very weak to absent, very shiny. Supraclypeal area, face above antennal fossae, vertex and genal area as in female but face, vertex and genal area duller.
Pronotum, mesoscutum, scutellum, propodeum and mesepisternum as in female except propodeal dorsal area without ridges. Wing venation as in female except vein 1st m-cu meets second submarginal cell near middle of cell; second submarginal cell much narrowed anteriorly. Tarsal claws with very large, inner, subapical tooth; hind tibia swollen at apex.
Metasomal sculpturing as in female but terga 1-4 very shiny, shagreening weak or absent, graduli weak or hidden, punctures small on tergum 5; pygidial plate absent; sterna 2-5 with small punctures separated by two or three puncture widths. Sternum 6 bent downward at apex, slightly emarginate.
Terminalia as in figures 9-13; note the following: gonocoxite with dorsal lobes short and broadly rounded, apex rather narrow; penis valve with small triangular, dorsal lamellae, apex short, thick, broadly rounded; sternum 7 with large apical notch; sternum 8 with apex slightly broader than neck region.
VESTITURE. — Generally as in female but longer, lacking pollen-collecting hairs, tergal hairs moderately long on tergum 1, hairs short, suberect on terga 2-5, apical fasciae on terga 2-4 weakly developed, especially in center on terga 2 and 3.
GEOGRAPHICAL VARIATION. — Throughout most of its range scurra has the apex of the hind tibia and the hind tarsus yellowish in color, but coastal populations have all dark legs. See Ribble (1973) for further details about this variation.
Andrena scurra X arabis X capricornis hybrids
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.
Please report text errors to: leah at discoverlife dot org.
The names listed above are junior synonyms (A. arabis, capricornis and scurra are all older names) and have hybrid holotypes. The hybrids treated in this section are those specimens which are distinctly intermediate between two or all three of the parental species (arabis, capricornis and scurra). The hybrids are often very variable at a single locality or between nearby localities. It would be very difficult to use Latin names for such populations. See Ribble (1973) for further details about this hybridization in Scaphandrena and for range maps.
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