Reprinted with permission of the American Entomological Society from:
LaBerge, W. E. 1980. A revision of the bees of the genus Andrena of the Western Hemisphere. Part X. Subgenus Andrena. Transactions of the American Entomological Society 106: 395-526.
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This moderate-sized pale eastern species is similar to pale specimens of Andrena thaspii with which the females are often confused. However, both sexes of mandibularis differ from those of thaspii by having a well-formed inferior basal tooth on each mandible, a simple labral process and no evident tergal pale fasciae; In addition the male of mandibularis has sternum 6 flat, not apically reflexed, and has flagellar segment 1 about as long as segment 2; The female of mandibularis has long tibial scopal hairs and a broad, apically round or blunt, pygidial plate.
FEMALE. MEASUREMENTS AND RATIOS. — N = 20; length, 8-11 mm; width, 2.5-3.5 mm; wing length, M = 4.16 ± 0.095 mm; FL/FW, M = 0.94 ± 0.004; FOVL/ FOVW, M = 3.14 ± 0.036.
INTEGUMENTAL COLOR. — Black except as follows: mandible with apical third or more rufescent; flagellar segments dark reddish-brown below; wing membranes hyaline, colorless or faintly infumate, veins reddish-brown; tibial spurs testaceous; distitarsi dark rufescent; tergal apical areas often dark rufescent; sterna with narrow apical areas hyaline, basal areas often with rufescent reflections.
STRUCTURE. — Antennal scape length equals first three flagellar segments; flagellar segment 1 about as long as following two segments, segment 2 shorter than 3 and about as long as broad; Eyes each about three and two-thirds times as long as broad, inner margins parallel; Mandible short as in frigida but with distinct basal inferior booth; Malar space and galea as in frigida; Maxillary palpus as in frigida but segmental ratio about as 0.9:1.0:0.8:0.8:0.7:0.7; Labial palpus as in frigida but ratio about as 1.0:0.6:0.6:0.6; Labral process entire, triangular or narrowly trapezoidal, swollen, shiny; labrum apical to process with weak median crista; Clypeus evenly rounded from side to side, with large round punctures of irregular size separated mostly by half a puncture width, impunctate midline broad in apical half; surface dulled by fine reticular shagreening; Supraclypeal area dulled by minute contiguous punctures; Face above antennal fossae with coarse longitudinal rugae and interrugal punctures; Facial fovea shallow, long, extending to below a line at lower margins antennal fossae, separated from lateral ocellus by three-fourths to one ocellar diameter, rarely less; Vertex short, above lateral ocellus usually equal to less than one ocellar diameter; surface opaque, punctate and tessellate; Genal area broad, in profile equal to one and one-third to one and one-half width of eye; surface moderately dulled by reticular shagreening and minute punctures, punctures not crowded in narrow shiny zone adjacent to eye.
Pronotum as in frigida; Mesoscutum and scutellum sculptured as in frigida; Propodeum with dorsal enclosure with fine reticular or irregular rugulae in basal third and often almost to apex medially, laterally tessellate; dorsolateral and posterior surfaces dulled by fine tessellation and crowded, shallow, obscure punctures; lateral surfaces coarsely tessellate; Mesepisternum as in frigida.
Metasomal terga 1-5 as in frigida but apical areas shinier, shagreening finer; Pygidial plate broad, apex rounded or blunt, internal raised triangular area distinct, widely separated from margins of pygidium; Sterna 2-5 sculptured as in frigida.
VESTITURE. — Entirely white or cinereous except as follows: facial fovea with upper half pale brown to ochraceous, inner surfaces tarsi yellow; Body vestiture moderately long to short; thoracic dorsum with hairs erect, sparse, not hiding surface; terga 1-5 without apical pale fasciae, basal areas with relatively sparse, erect, pale hairs; Tibial scopal hairs long, abundant, simple; propodeal corbiculum complete anteriorly with several long simple internal hairs; trochanteral flocculus complete.
MALE. MEASUREMENTS AND RATIOS. — N = 20; length, 7-10 mm; width, 1.5-2.5 mm; wing length, M = 3.43 ± 0.122 mm; FL/FW, M = 0.93 ± 0.006; FS1/FS2, M = 1.04 ± 0.008.
INTEGUMENTAL COLOR. — Black except with same exceptions as female but tergal apical areas often translucent reddish-brown.
STRUCTURE. — Antennae of moderate length; scape length about equal to first two flagellar segments; flagellar segment 1 about as long as segment 2, longer than broad; median segments about one and one-third times as long as broad; Eyes each about three and one-third times as long as broad, inner margins parallel; Mandibles decussate, when closed outer mandible extending beyond midlabrum by one-third its length; base with distinct inferior tooth; Malar space and galea as in female; Maxillary palpus as in female but segmental ratio about as 0.9:1.0:0.9:0.9:0.8:0.8; Labial palpus as in female; Labral process entire as in female but more reflexed, labrum without crista; Clypeus flattened, with small round punctures separated by half to one puncture width, sparser along midline and apicomedially, surface shiny except basally; Supraclypeal area and face above antennal fossae as in female; Vertex as in female but often slightly taller; Genal area broad, in profile at least twice as broad as eye, angulate posteriorly, with sparse minute punctures and fine shagreening moderately dulling surface.
Pronotum with dorsoventral ridge sharp, posterior to ridge shiny with a few longitudinal rugulae; surface otherwise opaque, tessellate; Mesoscutum and scutellum as in female; Propodeum as in female but dorsal enclosure usually with reticular rugulae more extensive and rougher and dorsoventral and posterior surfaces with shallow punctures more distinct.
Metasomal terga sculptured as in female; Tergum 7 without pygidial-like area; Sterna 2-5 sculptured as in frigida; Sternum 6 flat, apical margin weakly concave.
Terminalia as in figures 67-71.
VESTITURE. — White to pale ochraceous except inner surfaces tarsi pale yellow; vestiture generally sparse as in female; terga without apical pale fasciae, basal areas with short erect pale hairs; sterna 2-5 with distinct subapical fimbriae of long pale hairs, on each sternum fimbria slightly longer than apical area; sternum 6 with short erect pale hairs but not especially dense.
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 10 mm.; clypeus broader than long, with scattered irregular punctures on each side of a median impunctate line; facial foveae broad above, with pale brownish tomentum; lateral ocelli separated from margin of vertex by a space about equal to their diameter; cheeks subequal to eyes in width, very minutely and obscurely punctate; malar space evident but very short; basal segment of flagellum subequal to 2nd and 3rd combined; process of labrum subtriangular, the tip rounded; mandibles of ordinary length, scarcely at all overlapping; pubescence of head whitish, rather thin; thoracic integument dull, densely tessellate, only very obscurely punctate; enclosure of propodeum very finely rugose toward basal margin; thoracic pubescence entirely pale, rather thin; propodeal corbicula well developed, fringed anteriorly; trochanteral floccus well developed; tibial scopa of shorter, simple hairs, quite dense; all basitarsi slightly narrower than their respective tibiae; 2nd submarginal cell shorter than 3rd, receiving 1st recurrent beyond middle; abdominal terga dull, tessellate, impunctate, the apical margins slightly depressed, concolorous with discs, pubescence thin, entirely pale, the fasciae very poorly developed.
MALE — Length 8 mm.; clypeus quite flat, much broader than long, somewhat shining, minutely and rather sparsely punctate; lateral ocelli separated from margin of vertex by a space about equal to their diameter; cheeks much broader than eyes, angulate, angle opposite middle of eye (as in tridens, fig. 21), shining, minutely and rather sparsely punctate; malar space distinct but rather short; basal segment of flagellum only slightly exceeding each of the following segments in length; process of labrum subtriangular, much broader than long, the tip truncate, slightly incised; mandibles elongate, slender, flexed, overlapping nearly one-half, with a subapical inner tooth, and with a basal inferior projection; pubescence of head, thorax and base of abdomen rather long and dense, entirely pale, slightly yellowish above, more whitish below; thoracic integument dull, tessellate, the punctures very shallow and obscure; enclosure of propodeum smooth except for a few obscure basal rugae; all the basitarsi slender and elongate, considerably narrower than their respective tibiae; 2nd submarginal cell shorter than 3rd, receiving 1st recurrent toward apex; abdominal terga smooth, somewhat shiny, with sparse, very minute and obscure punctures, apical margins slightly depressed, mostly concolorous with the discs, pubescence rather short, entirely pale, fasciae entirely lacking; apical portion of sternum 8 rather slender, tip beyond the subapical ridge slightly broader than long, subtruncate and very slightly incised; penis valves expanded basally, excavated on each side beneath this expansion, gonocoxites rather broadly dilated apically, the gonocoxal lobes produced, very broadly rounded.
DISTRIBUTION — Minnesota to the New England states, Ontario and Nova Scotia, south to Georgia; March to July.
FLOWER RECORDS — Cornus, Crataegus and Malus. Robertson (1929) records this species from the following additional genera: Amelanchier, Claytonia, Hepatica, Prunus, Rhamnus, Rhus, Salix, Staphylea, Uvularia, Viburnum and Zanthoxylum. It is recorded on Kalmia and Pyrus by Brittain and Newton (1934).