Reprinted with permission of the American Entomological Society from:
LaBerge, W. E., Ribble, D. W. 1972. A revision of the bees of the genus Andrena of the Western Hemisphere. Part V: Gonandrena, Geissandrena, Parandrena, Pelicandrena. Transactions of the American Entomological Society 98: 271-358.
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This medium-sized species from California (Fig. 6) is highly' distinctive. The female can be readily recognized by the short appressed mesoscutal hairs and the facial fovea which is broader in the lower half than above (broadest at about level of upper margins of antenna! fossae). The male can easily be separated from other Parandrena by the almost complete lack of apicolateral teeth on the sixth sternum and the dark parocular areas. The male genal area is exceptionally broad and angular or lobed along the lower posterior margin in most specimens (best expressed in larger males). The male mandibles are very long and sickle-shaped. Allometric growth affects these head structures of the males, as is shown in a series of nineteen males from Acton, California.
FEMALE. MEASUREMENTS AND RATIOS. — N = 20; length, 9-12 mm; width, 3-4 mm; wing length, M = 3.63 ± 0.121 mm; FL/FW, M = 0.93 ± 0.004; FOVL/FOVW, M = 3.41 ± 0.036.
INTEGUMENTAL COLOR. — Black except as follows: mandible with apical third to half rufescent; flagellar segments 3- or 4-10 dark reddish-brown below; wing membranes slightly infumate, yellow, veins dark reddish-brown; tegula rufescent; tergal apices slightly rufescent; sternal apices hyaline; tibial spurs yellow.
STRUCTURE. — Antennal scape length equals first four and one-half to four and three-fourths flagellar segments; flagellar segment 1 equal in length to following two and three-fourths segments, otherwise as in andrenoides. Eyes, mandible and galea as in andrenoides. Labial palpus as in andrenoides but segmental ratio about as 1.0:0.8:0.5:0.5. Maxillary palpus as in andrenoides but ratio about as 1.0:1.0:0.7:0.7:0.6:0.6. Labral process small, triangular or with rounded apex (one specimen with extremely shallowly emarginate apex). Clypeus gently rounded from side to side; with small punctures separated by half to one puncture width laterally, become sparser towards midline, crowded subapically where surface appears transversely punctatorugose, midline impunctate; surface dulled by shagreening especially posteriorly and laterally (midline area of holotype shiny). Supraclypeal area with sparse minute punctures, surface moderately shiny to shiny (holotype), shagreening delicate. Face above antenna! fossae as in andrenoides but medially longitudinal rugulae interrupted by coarse punctures. Facial fovea broadest at level of upper margins of antennal fossae or just above, somewhat narrower above than below middle. Vertex extremely short, above lateral ocellus height equals less than half an ocellar diameter, in full facial view lateral ocelli not quite reaching vertex.
Pronotum with oblique suture not visible, otherwise as in andrenoides. Mesoscutum sparsely punctate, surface opaque, coarsely and regularly tessellate. Scutellum, propodeum, mesepisternum, wing venation and tibial spurs as in andrenoides.
Metasomal terga punctate as in andrenoides but surface moderately dulled by reticular shagreening (but shinier than in concinnula). Pygidial plate as in andrenoides but apex broadly rounded. Sterna as in andrenoides.
VESTITURE. — Generally pale ochraceous, somewhat darker on thoracic dorsum and vertex; facial fovea often with pale brown hairs in upper third; basitibial plate and scopal hairs below plate brown. Structure and distribution of hairs as in andrenoides except as follows: Mesoscutal hairs extremely short, appressed, sparse medially; propodeal corbicula with a few long, branched internal hairs; tergum 1 with pale apical fascia narrowly interrupted medially; terga 2-4 with pale apical fasciae not interrupted, short (half of apical area or less); sternal fimbriae weak.
MALE. MEASUREMENTS AND RATIOS. — N = 20; length, 7-10 mm; width, 1.5-2.0 mm; wing length, M = 3.12 ± 0.142 mm; FL/FW, M = 0.91 ± 0.006; FS1/FS2, M = 1.78 ± 0.041.
INTEGUMENTAL COLOR. — Black except as follows: clypeus yellow except narrow apical margin, notches or spots at tentorial pits and often along posterior border from tentorial pits to lateral angle (yellow to prostomial suture medially); flagellar segments 2-11 reddish-brown below; wing membranes hyaline, slightly infumate, veins and stigma reddish-brown; tegula rufescent; tergal apices slightly rufescent; sternal apices narrowly hyaline; tibial spurs yellow.
STRUCTURE. — Antennae moderately long, as in concinnula. Eyes each about three times as long as broad, inner margins distinctly converging towards mandibles. Mandible long, sickle-shaped, usually without inner apical tooth, apex usually reaches mandibular articulation of opposite side. Galea as in andrenoides. Labial palpus as in andrenoides but segmental ratio about as 1.0:0.6:0.4:0.6. Maxillary palpus as in andrenoides but ratio about as 1.0:0.8:0.8:0.6:0.6:0.6. Labral process small, trapezoidal with apex usually slightly emarginate, reflexed. Clypeus gently rounded from side to side, sculptured as in female but shinier. Supraclypeal area and face above antennal fossae as in female. Genal area broad to extremely broad, in profile equal in width to one and two thirds to two times width of eye or slightly broader, in most specimens angle at lower third along posterior margin produced into a rounded lobe (merely angular in small specimens). Vertex short but above lateral ocellus height equals one ocellar diameter or almost so (shortest in small specimens).
Pronotum without oblique suture, with several longitudinal rugulae, dulled by shagreening. Thoracic sculpturing as in female. Wing venation and tibia! spurs as in andrenoides.
Metasomal terga 1-5 punctate and shagreened as in female terga 1-4. Sternal sculpture as in andrenoides. Sternum 6 with apical margin shallowly emarginate, apicolateral corners angulate but not toothlike, not or scarcely reflexed. Terminalia as figured (Figs. 60-61); note the following; Genital capsule as in concinnula but dorsal process of gonocoxite obtuse apically. Sternum 7 angulate apicomedially with few weak hairs. Sternum 8 short, stout, apical part not as broad relative to neck region as in concinnula, hairs less stout.
VESTITURE. — Generally white to pale ochraceous. Distribution and form of hairs as in andrenoides except as follows: more sparsely haired in general; terga 1-5 with short, thin, pale, apical fasciae but narrowly interrupted medially on tergum 1 and often on tergum 2; sternal subapical fimbriae weak.
REMARKS. — The single male collected at Davis, California, has shorter mandibles with a distinct inner tooth as in concinnula or andrenoides. This is a small male and this modification may be a result of allometric growth which affects other head characters, especially the vertex and the genal area as described above. However, this is the only male in which the mandibles are not long and sickle-shaped. It is possible that this specimen represents hybridization between bucculenta and some other species, possibly concinnula. The pronotum shows some resemblance to concinnula but the tergal sculpturing and the shape of the sixth and eighth sterna are typical of bucculenta.