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.
Please report text errors to: leah at discoverlife dot org.
Andrena wilkella is a large, readily recognized bee from Northeastern North America. The female has slightly elongated punctures on the flattened clypeus, highly punctate metasomal terga, roughened but not rugulate propodeal enclosure, and pollen collecting hairs as in the subgenus Thysandrena. The males are similar but the clypeal punctures tend to be round and the sternum 6 is flat and slightly emarginate. In general, the male looks like a punctate Thysandrena with a flattened clypeus and short first flagellar segment of an Opandrena with a black clypeus.
FEMALE. MEASUREMENTS AND RATIOS. — N = 20; length, 10 - 12 mm; width, 3-4 mm; wing length, M = 3.96 ± 0.112 mm; FL/FW, M = 0.096 ± 0.004; FOVL/FOVW, M = 2.98 ± 0.040.
INTEGUMENTAL COLOR. — Black except as follows: mandible with apical fourth to half dark rufescent; flagellar segments below dark brown to black; wing membranes hyaline, veins reddish brown to dark brown; hind tibiae and basitarsi and middle basitarsi often bright orange-red (about 50% of specimens); tibial spurs testaceous.
STRUCTURE. — Antennal scape as long as first three and one-half flagellar segments; flagellar segment 1 as long as segments 2 plus 3; segments 2 and 3 quadrate, median segments slightly longer than broad. Eyes each 4 times as long as broad or slightly longer, inner margins parallel. Mandibles as in nasonii. Galea with outer margin slightly concave, surface dulled by fine tessellation, with scattered minute punctures. Maxillary palpus longer than galea by last two segments, segmental ratio about as: 1.0:1.0:0.7:0.6:0.4:0.7. Labial palpus with last three segments relatively long and first segment relatively short, ratio about as: 1.0:0.7:0.6:0.7. Labral process trapezoidal, slightly constricted before apex, emarginate apically, surface basad of apical teeth with fine curved rugulae, shiny; surface below process flat, shiny, with median crista. Clypeus markedly flattened, with elongate punctures separated mostly by one puncture width or less, surface dulled by shagreening. Supraclypeal area dulled by minute punctures, shagreening and fine longitudinal rugulae. Face above antennal fossae dulled by longitudinal rugulae and interrugal punctures. Facial fovea broad, shallow, separated from lateral ocellus by one ocellar diameter or slightly less. Vertex above lateral ocellus equal to about one ocellar diameter or slightly more, dull, shagreened. Genal area slightly broader than eye in profile, dulled by fine tessellation and fine longitudinal rugulae.
Pronotum without humeral angles or dorsoventral ridges, dulled posteriorly to moderately shiny anteriorly, shagreened. Mesoscutum with small round punctures separated mostly by half to one puncture width, slightly sparser posteromedially, surface dulled by tessellation. Scutellum similar. Metanotum dull, densely tessellate. Propodeum with dorsal enclosure with irregular rugulae forming small locular areas except tessellate apically and base often with a row of short longitudinal rugulae; dorsolateral areas roughened by large punctures and fine tessellation. Fore wing with vein r longer than 4 or 5 vein widths.
Metasomal tergum 1 with basal area with small crowded punctures separated by less than half a puncture width basally, by about one puncture width near apical area, apical area with crowded, shallow punctures, surface dulled by fine reticular shagreening. Terga 2-4 similar but basal areas more densely punctate apically near apical areas. Pygidial plate V-shaped with distinct raised internal triangle. Sterna 2-5 with basal area punctures small, crowded, similar to tergal punctures, surfaces moderately shiny, finely shagreened.
VESTITURE. — Ochraceous except as follows: metasomal terga 2-4 with basal area hairs dark brown, apical areas with narrow white fasciae broadly interrupted medially on tergum 2, narrowly so on tergum 3, entire to narrowly interrupted on tergum 4; terga 5 and 6 with vestiture largely pale; hind tibiae and basitarsal scopal hairs golden.
MALE. MEASUREMENTS AND RATIOS. — N = 20; length, 9-11 mm; width 2-3 mm; wing length, M = 3.67 ± 0.161mm; FL/FW, M = 1.02 ± 0.005; FS1/FS2, M = 0.71 ± 0.008.
INTEGUMENTAL COLOR. — As in female except as follows: mandibles with apical fourth to third rufescent; metasomal terga 2-5 with apical areas slightly translucent apically; sterna 2-5 with apical areas hyaline, colorless to yellow basally; hind basitarsus usually rufescent, tibia dark.
STRUCTURE. — Antennal scape as long as first two flagellar segments or slightly longer; flagellar segment 1 distinctly shorter than segment 2, often about as long as broad; segments 2-10 much longer than broad. Eyes each three and one-half times as long as broad or slightly longer, inner margins converging slightly toward mandibles. Galeae, mandibles, and labral process as in female. Maxillary palpus as in female but segmental ratio about as 0.8:1.0:0.8:0.7:0.7:0.8. Labial palpus as in female but ratio about as 1.0:0.7:0.6:0.7. Clypeus as in female but not quite as flat and punctures less elongate. Supraclypeal area, face above antennal fossae, vertex, and genal areas as in female.
Thoracic form and sculpturing as in female. Metasomal terga 1 - 5 as in female terga 1 - 4 but punctures slightly larger and sparser. Sterna 2-5 sculptured as in female terga 2-4 but punctures slightly larger. Sternum 6 not reflexed, apical margin gently emarginate. Terminalia as in Figures 47 - 51.
VESTITURE. — In general as in female but tergal apical fasciae interrupted medially on terga 2-5; lacking pollen collecting hairs.
Reprinted with permission from: Mitchell, T.B. 1960. Bees of the Eastern United States. North Carolina Agricultural Experiment Station Technical Bulletin No. 141.
FEMALE. — Length 11 mm.; clypeus flattened, projecting slightly less than one-half below suborbital line, dull and tessellate, punctures shallow but rather close and fine on each side of a very narrow and indefinite, median, impunctate line; facial foveae broad, nearly filling area between eyes and ocelli, covered with bright ochraceous tomentum; space between margin of vertex and lateral ocelli nearly equaling distance between ocelli; cheeks broader than eyes, rounded posteriorly, smooth and somewhat shining, punctures very minute and obscure; malar space very short; basal segment of flagellum subequal to 2nd and 3rd combined; process of labrum broadly subtriangular, narrow apex subtruncate, very slightly emarginate; pubescence of head and thorax brownish-ochraceous above, somewhat paler below and on legs, rather short and dense on dorsum of thorax; thoracic integument dull and tessellate, punctures of scutum shallow but rather coarse and close, somewhat more widely separated in center of disc, those on scutellum fine and well separated. surface more shining; pleural punctures obscure; triangle of propodeum very finely rugoso-striate; propodeal corbicula extremely short and poorly developed, without a distinct, anterior fringe, pale ochraceous; trochanteral floccus well developed, of moderate length, whitish; hind tibiae becoming quite broad apically, scopa quite dense, hairs simple, of moderate length, entirely pale ochraceous; all basitarsi slightly narrower than their respective tibiae; 2nd submarginal cell much shorter than 3rd, receiving 1st recurrent at middle; abdominal terga dull, very closely, finely and rather deeply punctate, apical depressed areas rather deep laterally, shallow medially, occupying somewhat less than one-third median length of discs, becoming very narrowly reddened along rims, discs almost completely bare of pubescence but with rather dense and narrow, apical ochraceous fasciae on terga 2-4, that on tergum 2 widely interrupted, slightly so on 3, tergum 5 with a rather narrow, brownish-ochraceous, apical fimbria.
MALE. — Length 10 mm.; clypeus somewhat produced but flattened medially, projecting nearly one-half below suborbital line, surface shining, deeply and closely punctate except along narrow, median area, where they are rather sparse; space between margin of vertex and lateral ocelli only slightly shorter than distance between ocelli; cheeks not much broader than eyes, rounded posteriorly, somewhat shining, punctures minute and close, rather indistinct; malar space very short; basal segment of flagellum considerably shorter than 2nd segment, not much longer than apex is broad; process of labrum very short and broad, apex narrowly and shallowly emarginate; mandibles quite short, rather straight, with a distinct, inner, subapical tooth, pubescence of head, thorax and legs entirely pale ochraceous; thoracic integument dull and tessellate, punctures of scutum shallow, moderately coarse, quite close except in center of disc, where they are more widely separated, well separated but not sparse on scutellum, which is somewhat more shining; pleural punctures obscure, surface more nearly subrugose; enclosure of propodeum finely subrugose; all basitarsi slender and elongate, considerably narrower than their respective tibiae; 2nd submarginal cell much shorter than 3rd, receiving 1st recurrent near middle; abdominal terga dull, closely, deeply and rather finely punctate, apical depressed areas rather narrow and shallow, obscurely reddened toward rims, discal pubescence very short, suberect, entirely pale, forming rather obscure, narrow, whitish, apical fasciae toward sides of terga 2-4; apical portion of sternum 8 rather robust, without a distinct, ventral protuberance, apex rather broadly rounded, apical half quite densely pubescent beneath; penis valves very slender, the base slightly enlarged, gonocoxites quite broad, only slightly dilated apically, gonocoxal lobes not produced.
DISTRIBUTION. — Holarctic, occurring in North America from Nova Scotia through Quebec and the New England states to Wisconsin, eastward through Ohio to Virginia and Maryland; April to August.
FLOWER RECORDS. — Crataegus, Malus, Rhodora, Rubus, Trifolium and Vaccinium. According to Brittain and Newton (1933 & 1934) wilkella also visits Achilles, Amorpha, Brassica, Cirsium, Daucus, Epilobium, Fragaria, Leontodon, Philadelphus, Pinus, Prunus, Raphanus, Rhododendron, Solidago, Stellaria and Taraxacum.