Reprinted with permission of the American Entomological Society from:
LaBerge, W. E. 1989. A revision of the bees of the genus Andrena of the Western Hemisphere. Part XIII. Subgenera Simandrena and Taeniandrena. Transactions of the American Entomological Society 115: 1-56.
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This is a highly variable species from the western states. It is similar to Andrena angustitarsata but has highly plumose, moderately long, scopal hairs in the female and more coarsely sculptured propodeum in both sexes.
FEMALE. MEASUREMENTS AND RATIOS. — N = 20; length, 8-12 mm; width, 2.5-4.0 mm; wing length, M = 3.81 ± 0.407 mm; PL/ FW, M = 0.93 ± 0.070; FOVL/FOVW, M = 3.29 ± 0.047.
INTEGUMENTAL COLOR. — Black except as follows: mandible with apical third or less dark rufescent; flagellar segments dark brown to black below, outer six to eight segments occasionally dark rufescent; wing membranes hyaline, veins dark reddish brown to black, pterostigma usually dark; metasomal terga with apical areas black to slightly rufescent apically, sterna extremely narrowly hyaline apically; distitarsi dark reddish brown to black; tibial spurs testaceous.
STRUCTURE. — Antennal scape as long as first three and a half to four flagellar segments; flagellar segment 1 as long as segments 2 and 3 together or slightly longer; segments 2 and 3 subequal and each slightly broader than long. Eyes each about 4 times as long as broad, inner margins parallel. Malar space, mandibles, and galeae as in nasonii. Maxillary palpus as in nasonii but segmental ratio about as 1.0:1.0:0.8:0.8:0.6:0.8. Labial palpus as in nasonii but segmental ratio about as 1.0:0.6:0.3:0.4. Labral process trapezoidal to rounded apically, rarely weakly emarginate; surface dull to shiny; labrum without cristae. Clypeus moderately flattened, punctate but punctures often obscured by shagreening. Supraclypeal area, face above antennae, and facial foveae as in nasonii. Vertex above lateral ocellus usually equals one ocellar diameter, less in smaller specimens, and as much as one and one-half ocellar diameter in some large specimens. Genal area as in nasonii.
Pronotum and thoracic sculpturing as in nasonii. Fore wing with venation as in nasonii, vein r usually equal to two or three vein widths.
Tergal sculpturing as in nasonii but terga 2-4 with basal area punctures absent. Pygidial plate as in nasonii but internal triangular area weakly raised. Sterna 2-5 sculptured as in nasonii.
VESTITURE. — White to pale ochraceous. Tibial scopal hairs moderately long, plumose along anterior and posterior margins, narrow median zone with simple hairs. Propodeal corbiculum and trochanteral flocculus as in nasonii. Metasomal terga 2-4 with pale apical fasciae as in nasonii but usually weaker, that on tergum 2 interrupted medially by at least one-third width of tergum.
MALE. MEASUREMENTS AND RATIOS. — N = 20; length, 6-11 mm; width, 1.0-2.5 mm; wing length, M = 3.22 ± 0.389 mm; FL/FW, M = 1.03 ± 0.010; FSI/FS2, M = 1.08 ± 0.025.
INTEGUMENTAL COLOR. — As in female except as follows: mandible with apical fourth or less dark rufescent; flagellum below dark brown to black; metasomal terga with apical areas usually yellowish brown to translucent or narrowly hyaline apically; distitarsi often dark rufescent.
STRUCTURE. — Antennal scape as long as first two to two and three-fourths flagellar segments; flagellar segment 1 usually about as long as segment 2 and slightly shorter than 3, occasionally distinctly longer than segment 2; flagellar segment 2 usually shorter than 3 and about as long as broad; median segments longer than broad. Malar space, galeae, and mandibles as in female. Maxillary palpus as in female but segmental ratio about as 1.0:1.0:0.7:0.7:0.6:0.6. Labial palpus as in female but segmental ratio about as 1.0:0.6:0.4:0.5. Labral process as in female but often slightly emarginate apically, usually shiny; labrum without cristae. Clypeus dull, opaque, finely and densely tessellate, with punctures obscured by tessellation. Supraclypeal area, face above antennal fossae, vertex and genal area as in female.
Pronotum as in female. Thoracic sculpturing much as in female but thoracic dorsum with punctures usually absent or barely visible, never shiny; propodeum with sculpturing as in female but enclosure usually more coarsely rugulate. Metasomal sculpturing as in female but terga with basal area never with distinct punctation; terga 2-5 with basal area punctures more sparse; sternum 6 flat, shallowly emarginate apically. Terminalia as in Figures 42-46.
VESTITURE. — White to ochraceous except as follows: vertex and face along inner margins eyes often black; terga 3-5 with basal area hairs usually brown; terga 2-5 with pale apical fasciae present, usually white, rarely interrupted medially on tergum 2. Sterna without subapical fimbriae.
VARIATION. — Andrena pallidifovea is exceptionally variable in size, color, and integumental sculpture. A few of the morphological types have been recognized with scientific names. Some of this variation seems to be associated with geography and/or habitat. The smallest specimens were segregated by P.H. Timberlake and given a manuscript name. Small specimens often have slightly paler flagella and usually pale ochraceous vestiture. However, these small specimens are not concentrated in any one area but occur throughout most of the range of this species. Also, there are intermediates in size throughout the range of pallidifovea.
Among the smaller females from California are a number of specimens with highly punctate metasomal terga. The first tergum has the basal area with distinct round punctures separated by one to two puncture widths or less, terga 3 and 4 have the basal area punctures more crowded. Punctate females of this kind are especially abundant in southern California and along the coast north to Santa Clara County. All females from Santa Cruz Island, Santa Barbara County, are punctate. Prof. P. H. Timberlake recognized this variety as Andrena (Stenandrena) essigi in 1951. The males associated with these specimens are not distinguishable from males associated with the typical pallidifovea. Three females from Baja California del Norte are punctate in this manner but are larger in size, being about equal to the average size for the species.
About 50 female specimens from various localities in California, but especially from montane areas, are marked by having a shiny mesoscutum and scutellum. These areas have minute, sparse punctures, but the shagreening usually present is absent or extremely weak. Males collected with these females are not so marked and are indistinguishable from other pallidifovea males. In several instances, these shiny females were collected in longer series with normal females having the mesoscutum and scutellum dull.
The largest of the female specimens frequently have the vertex above the lateral ocellus equal to more than one ocellar diameter. Most specimens of pallidifovea have the vertex equal to about one ocellar diameter or slightly shorter. The smallest specimens frequently have the shortest vertices. Males in the same series with these large females with tall vertices frequently have the first flagellar segment distinctly longer than the second segment. Smaller males have the first flagellar segment about equal in length to the second. At first this seemed to be an allometric change, but short first flagellar segments do occur in large specimens and long first flagellar segments occur in a few of the small males.
The above variation does not seem to be strongly correlated with geography, with the exception that all of the Santa Cruz Island specimens are small and the females punctate. This author, therefore, concludes that named geographic races or subspecies are not indicated.