Reprinted with permission from the University of Nebraska State Museum from:
Ribble, D. W. 1968. Revisions of two subgenera of Andrena, Micrandrena Ashmead and Derandrena new subgenus (Hymenoptera: Apoidea). Bulletin of the University of Nebraska State Museum 8: 1-124.
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In spite of being common and wide spread in western North America little has been published on piperi. Judging from determined specimens, piperi is seldom confused with other species, although Viereck misassociated the sexes (Timberlake, 1951).
Andrena piperi is a coarsely shagreened black species with only slight metallic reflections which are especially noticeable on the female clypeus. The female has short plumose hairs that on the mesoscutum have a moss-like appearance and on abdominal terga 2-4 a dusty appearance. The hind tibia is relatively wide with long scopal hairs; the anterior-most hairs bend over and point posteriorly, most scopal hairs are thus orientated in the same direction and obscure the surface of the tibia. The male has a yellow clypeus, dull, relatively long antennae, flagellar segment 1 slightly longer than 3 and segment 3 slightly longer than 2. The male abdomen has many short, plumose hairs but it does not reach the dusty condition found in the female.
The descriptions below are based on a male (May 7, 1907) and a homotype female (May 2, year not given) from the type locality, Pullman, Washington. One thousand three hundred and fifty-one other specimens were also examined.
FEMALE. MEASUREMENTS AND RATIOS. — Length, 8.0 mm; width of mesothorax, 2.1 mm; wing length from tegula, 5.6 mm; facial length/width, 0.96; foveal length/width, 5.14.
INTEGUMENTAL COLOR. — Black with slight dark blue-green or purplish reflections except: tip of mandible deep red; eye grey; flagellum red-brown below at tip; wings amber, veins dark amber, pterostigma amber; tegula dark amber; terga with narrow amber apices; sterna with broader amber apices; distitarsi amber at tip; tibial spurs light amber; claws amber.
STRUCTURE. — Antenna reaching slightly beyond tegula; scape reaching to one and one-half ocellar distance from middle ocellus, slightly longer than flagellar segments 1-4; flagellar segment 1 slightly longer than 2 and 3 together, tapered toward base; segment 2 and 3 subequal in length, each shorter than 4, both slightly tapered; middle segments wider than long; ultimate segment rounded in lateral view, pointed in dorsal view, almost twice as long as broad. Eye about three times as long as broad in anterior view, inner eye margins converging slightly below. Malar space about eight times as wide as long. Mandibles decussate in repose, extending nearly to opposite corner of labrum; apex rounded; inner rounded subapical tooth present. Galea with outer margin below palpus expanded into a distinct but rather narrow lobe, tapering to a narrowly rounded apex; both margins curving downward; surface shiny, with fine reticular shagreening which form shallow, flat bottomed pits. Maxillary palpus with segments in ratio of about 1.1:1.6:1.2:1.3:1.0:1.3; segments tapering toward bases; segment 6 slender, flattened; segment 5 and 6 extending beyond galea. Labial palpus with segments in ratio of about 2.5:1.0:1.0:1.4; segments tapering toward bases; segment 1 curved; segment 4 slender, flattened; segments 3 and 4 attached subapically. Labrum about three times as wide as long, outer margin broadly rounded from side to side; process one-fifth as wide and half as long as entire labrum, raised, shiny, sides nearly parallel, apex truncate. Clypeus almost twice as wide as long, protruding beyond lower margin of eye by about two-thirds width of eye in lateral view, punctures more numerous at sides, punctures obscured by reticular shagreening much like that on galea except pits larger. Supraclypeal area with sculpturing less even and coarser than clypeus. Genal area in lateral view nearly as wide as eye, surface with reticular shagreening. Vertex elevated above eyes, extending past lateral ocellus by less than one ocellar width; surface between ocelli rough, with irregular shagreening, punctures indistinct; surface above fovea smoother, more shiny, punctures indistinct, with reticular shagreening. Face above antennal fossae moderately shiny, with indistinct punctures, vertical rugae, irregular shagreening. Frontal line weak. Facial fovea not reaching upper eye margin, rounded dorsally, dorsally two-thirds width of eye, inner margin distinctly separated from eye margin especially medially.
Pronotum without humeral angle; sutures extending vertically and anteriorly from pit at base of posterior pronotal lobe, anterior suture indistinct and not reaching anterior margin of pronotum; pronotal surface with reticular shagreening. Mesoscutum with indis¬tinct punctures, surface with reticular shagreening; parapsidal lines distinct, about 0.02 mm long. Tegula oval, with minute reticular shagreening. Scutellar and metanotal surfaces similar to mesoscutal. Propodeum with dorsal enclosure concave on anterior margin, posterior margins meeting to form a "V", enclosure sloping gently over anterior two-thirds, posterior third vertical, surface with rather even reticular shagreening; propodeum with posterior surface divided by deep vertical sulcus, posterior and lateral surfaces not separated by carinae, posterior and dorsolateral areas raised slightly above enclosure, punctures indistinct, shagreening irregular and closer than center of enclosure; corbicular surface with few indistinct punctures, shagreening less granular, more even and further apart than on enclosure. Mesepisternum with surface similar to mesoscutum. Metepisternum similar to corbicular surface but impunctate below, shagreening closer above. Middle basitarsus nearly parallel-sided. Hind tibia broadened, nearly twice as wide as basitarsus. Claws with large tooth on inner margin. Anterior tibial spur bent, with broad lamella along basal half of inner margin, spur serrate along distal half of inner margin; middle tibial spur long, slender, nearly straight, serrate along inner margin; hind tibial spurs long, slender, nearly straight; posterior spur slightly longer; spurs serrate along posterior margins. Wings with pterostigma large, nearly twice as wide as prestigma; three submarginal cells; first transverse cubital vein ending about two vein widths from pterostigma; first m-cu vein ending near middle of second submarginal cell.
Metasomal terga moderately shiny, punctures indistinct, surface with fine reticular shagreening. Pygidial plate narrowly rounded, with edges turned upward, center not raised, with reticular shagreening. Sternum 1 emarginate. Sterna with many fine punctures, punctures partly obscured by fine reticular shagreening.
VESTITURE. — White except: some hairs on tip of abdomen and tarsi amber; facial fovea brownish especially above. Hairs abundant, long, straight, very plumose except: those of facial fovea short; few minute, simple hairs on eye; dorsum of thorax with dense short hairs having a moss-like appearance; propodeal corbicular hairs few, simple in center, along dorsal margin hairs curved; terga 2-4 hairs (except for apical fasciae) short, plumose, giving the abdomen a dusty appearance, with apical fasciae very distinct, interrupted medially on terga 1 and 2, partly interrupted on 3; sterna 2 to 5 hairs short, mostly simple, except subapical fimbriae of long, plumose hairs, longest hairs behind apical row; tibial scopa with long, simple hairs, anterior- and posterior-most hairs may have a few branches, hairs along anterior margin curved posteriorly; other leg hairs variable in structure.
MALE. MEASUREMENTS AND RATIOS. — Length, 6.5 mm; width of mesothorax, 1.8 mm; wing length from tegula, 5.2 mm; facial length/width, 0.90; flagellar segment 1/segment 2, 1.5.
INTEGUMENTAL COLOR. — Black with slight dark blue-green or purplish reflections except: tip of mandible deep red-amber; eye grey; clypeus yellow, with two small, lateral hyaline spots; flagellum dark brown below; wing and tegula as in female; terga and exposed sterna with amber apices; distitarsi slightly amber; tibial spurs light amber; claws red-amber.
STRUCTURE. — Antenna reaching to propodeum; scape reaching to within one ocellar distance of medium ocellus, slightly longer than flagellar segments 1-3; segment 1 one and one-third times as long as 2, nearly as long as 3, tapered toward base; segment 2 not noticeably tapered; middle segments slightly longer than broad; ultimate segment rounded in lateral view, pointed in dorsal view, slightly less than twice as long as broad. Eye three and a half times as long as broad in anterior view, inner eye margins distinctly convergent below. Malar space about seven times as wide as long. Mandible and galea as in female. Maxillary palpus as in female but segments in ratio of about 1.3:1.8:1.5:1.5:1.0:1.8. Labial palpus as in female but segments in ratio of about 2.7:1.0:1.3:2.7. Labrum slightly less than twice as wide as long, apical margin broadly rounded from side to side; process about half as wide and half as long as entire labrum, raised, shiny, slightly expanded toward base, apex very distinctly emarginate. Clypeus twice as broad as long, shiny, protruding beyond lower margin of eye by about half width of eye in lateral view, very punctate, surface with fine reticular shagreening. Supraclypeal area, genal area, vertex and face above antennal fossae as in female.
Mesosoma as in female except hind tibia unmodified.
Metasoma as in female except: pygidial plate absent; posterior margin of sternum 6 emarginate and flexed ventrad.
Sternum 7 distinctly emarginate at apex, producing two large, narrowly rounded lobes, each lobe bearing numerous long, branched setae (fig. 4). Sternum 8 nearly flat from side to side; base flexed ventrad, expanded into large plate (fig. 5); apex expanded, weakly bilobed; shaft shorter than base; sternum with apical half setose, setae dense, mostly long, branched, curving and not reaching beyond apex. Gonocoxite bent downward; apex expanded in lateral view, dorsolateral part with many branched setae; dorsal lobes large, long, broadly rounded at apex. Penis valve bent downward, apex rounded in dorsolateral view, medially greatly expanded (figs. 1-3).
VESTITURE. — Body hairs white. Hairs otherwise as in female except: clypeus with longer and more plumose hairs, producing a distinct "beard"; facial fovea absent; dorsum of thorax with long hairs; hairs on abdominal terga longer, abdomen with only weak dusty appearance; apical fasciae very weak, interrupted on terga 1-4; apex of sternum 6 with tuft of hairs; hairs specialized for pollen collecting absent.
VARIATION. — A very small male (wing length, 4.4 mm) was collected at Blue Creek, Utah. Other specimens from the same locality are larger and some of them normal in size. Small specimens, approaching the Blue Creek male in size, are found at other localities. The first transverse cubital vein may end two to three vein widths from the pterostigma in either sex. The pterostigma is either light or dark amber. In the female the labral process varies from truncated to rounded at the apex. The tarsal hairs in the female are sometimes white rather than amber.