Reprinted with permission of the American Entomological Society from:
LaBerge, W. E., Bouseman, J. K. 1970. A revision of the bees of the genus Andrena of the Western Hemisphere. Part III. Tylandrena. Transactions of the American Entomological Society 96: 543-605.
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This large spring bee is rare in collections. It is closely related to A. perplexa which it superficially resembles very closely. It also closely resembles an as yet undescribed species of the subgenus Melandrena with which it has been confused by most authors. The female of wilmattae can be separated from that of perplexa by three characters: wilmattae lacks the three prominent labral crista present in perplexa and has a transverse, subapical, shiny sulcus rather than two median shiny depressions; the propodeal corbicula lacks plumose hairs anteriorly; the terga (especially 2 and 3) are slightly more densely punctate. The male of wilmattae differs from that of perplexa principally by having a flatter labral process not prominently depressed medially and by the sixth sternum lacking the longitudinal shallow sulcus. Both sexes have the pronotum shaped slightly differently from that of perplexa, as described below.
FEMALE. MEASUREMENTS AND RATIOS. — N = 20; length, 10-14 mm; width, 3.0-4.5 mm; wing length, M = 4.66 ± 0.185 mm; FL/FW, M = 0.93 ± 0.007; FOVL/FOVW, M = 2.96 ± 0.024.
INTEGUMENTAL COLOR. — Black except as follows: mandible with at least apex rufescent; flagellar segments 3-10 reddish-brown below; wing veins dark brown to reddish-brown, membranes moderately infumate, yellowish-brown; distitarsi and usually basitarsi red to orange.
STRUCTURE. — Antennal scape length equals almost flagellar segments 1-4; flagellar segment 1 equals segments 2 plus 3 and one-third of 4, segment 2 slightly shorter than 3 and 3 shorter than 4, segments 2 and 3 shorter than broad or quadrate, 4-10 longer than broad. Eye, malar space, mandible and galea as in perplexa. Maxillary palpus as in perplexa but segmental ratio about 0.9:1.0:0.7 :0.7 :0.6: 0.5. Labial palpus as in perplexa but ratio about 1.0: 0.5:0.3:0.4. Labral process two and one-half to three times as broad at base as long, entire, slightly thickened near apex; labrum without prominent crista apically, with a transverse, shiny, subapical sulcus which may have several weak internal crista near base visible under high magnification, not forming two prominent depressions below process. Clypeus as in perplexa but surface entirely dulled by fine shagreening and median impunctate line often complete. Supraclypeal area, genal area, vertex and face above antennae as in perplexa.
Pronotum much as in perplexa but ear-shaped lobe of humeral angle set closer to mesonotum and lower-lateral part shiny and unshagreened posteriorly. Thoracic sculpturing as in perplexa except as follows: propodeal dorsal enclosure usually with irregular rugulae over more than half of surface (rarely less than half); mesepisternal punctures separated mostly by two puncture widths or less. Wing venation as in perplexa but second submarginal cell narrowed above, along anterior margin no longer or only slightly longer than third cell and along posterior margin slightly shorter than third cell. Tergal sculpturing much as in perplexa but denser; terga 1-4 with apical areas with basal three-fourths (or almost) with small punctures separated mostly by one to two puncture widths, tergum 1 with basal area punctures separated mostly by two puncture widths; terga 2-4 with basal area punctures separated mostly by half a puncture width or less (sparser on tergum 4), apical area surfaces moderately dulled by fine tessellation, basal area surfaces shiny, lightly or not at all shagreened. Pygidial plate and sterna as in perplexa.
VESTITURE. — Generally pale ochraceous, slightly darker to rufescent on vertex and thoracic dorsum. Otherwise as in perplexa but propodeal corbicula without plumose hairs anteriorly and tarsal hairs pale.
MALE. MEASUREMENTS AND RATIOS. — N = 20; length, 8.5-12.0 mm; width, 2.5-4.0 mm; wing length, M = 3.86 ± 0.351; FL/FW, M = 0.90 ± 0.004; FS1/FS2, M = 1.44 ± 0.024.
INTEGUMENTAL COLOR. — Black except as follows: mandible rufescent at least apically; flagellar segments 2-11 red or reddish-brown below; wing veins brown to reddish- or yellowish-brown (pterostigma usually pale); tarsi usually and apex of tibiae often rufescent.
STRUCTURE. — Antennae moderately long, in repose reaching just beyond posterior margins tegulae; scape length equals first two and three-fourths flagellar segments; flagellar segment 2 distinctly shorter than 3, slightly longer than broad or quadrate, segment 3 subequal in length to segments 1 and 4-10, longer than broad. Eye, malar space, mandible and galea as in perplexa. Maxillary palpus as in perplexa but segmental ratio about 1.0:0.9:0.5:0.5:0.4:0.5. Labial palpus as in perplexa but ratio about 1.0:0.5:0.4:0.3. Labral process narrow, less than twice as broad at base as long, curved, slightly emarginate apically, slightly thickened at apical ends but not grooved medially. Clypeus as in perplexa but surface shinier, finely shagreened. Genal area, supraclypeal area, face and vertex as in perplexa.
Pronotum as in perplexa but humeral angle not forming a lateral ear-shaped lobe, set closer to mesonotum as in female. Thoracic sculpturing as in perplexa but propodeal dorsal enclosure usually slightly more extensively rugulose or roughened. Terga 1-5 with apical areas each with basal half or slightly less with scattered punctures. Tergum 1 with basal area with small punctures separated by two to three or more puncture widths (occasionally practically impunctate), surface shiny. Terga 2-5 with basal areas with punctures separated mostly by two puncture widths or more (rarely less), surfaces shiny. Sterna as in perplexa but punctures slightly more abundant and sternum 6 without median longitudinal sulcus.
Terminalia as figured (Figs. 26-30) but note the following: penis valves more expanded basally than in perplexa; volsellae larger; gonocoxite with apical lobe with short sparse hairs; sternum 8 with apical margin straight, extremely feebly emarginate medially; sternum 8 with apical part set off rather abruptly from basal part but with short stout hairs medially as in erythrogaster.
VESTITURE. — Generally as in perplexa but sternum 6 without distinct subapical fimbria of dense short hairs.
Reprinted with permission from: Mitchell, T.B. 1960. Bees of the Eastern United States. North Carolina Agricultural Experiment Station Technical Bulletin No. 141.
Described using the synonymous name: Andrena acra Mitchell
MALE. — Length 10 mm.; face nearly as long as distance between eyes; clypeus short, rather flat, finely punctate, median punctures distinctly but not widely separated, becoming quite densely crowded at extreme sides: vertex broad, lateral ocelli separated from its hind margin by nearly twice their diameter, surface dull but rather smooth, punctures very fine and obscure; cheeks very broad, with a rounded posterior angle about opposite middle of eye; malar space linear; process of labrum narrow, the tip somewhat produced and deeply impressed medially; basal segment of flagellum dark, slightly longer than segment 2, it and the following segments brownish-testaceous beneath, becoming piceous above; mandibles slender and elongate, with a subapical inner tooth near tip, upper face deeply grooved from this inner tooth to near the base, the pair overlapping about two-thirds when closed; pubescence of entire head pale ochraceous to whitish, rather thin but elongate, that on thorax similarly colored but more dense, that on dorsum bright ochraceous, entirely pale ochraceous on legs; scutum dull anteriorly, becoming somewhat shining and more sparsely punctate posteriorly, punctures shallow and indistinct, those on scutellum sparse on each side of center; pleura dull, with shallow, indistinct but rather close punctures; propodeal triangle with a few fine basal striations; the more basal segments of legs black, tarsi more ferruginous; wings subhyaline, veins and stigma ferruginous, second submarginal cell slightly shorter than 3rd; tegulae piceous; abdominal terga smooth and shining, with fine, evenly distributed punctures, these sparse on basal tergum, becoming somewhat closer, but still well separated on segments 2 and 3, sparse again on 4 and 5; apical margins of segments 2-5 somewhat depressed towards sides apically, these areas somewhat coppery, discal pubescence entirely pale, very short and inconspicuous, fasciae not developed; sternum 7 produced and subtruncate medially; sternum 8 narrowly truncate apically; penis valves bulbous at base, becoming slender apically, not excavated, gonocoxites slightly expanded apically, gonocoxal lobes moderately produced, rounded at tip.
TYPES. — Holotype: Male, Gull Lake Biol. Sta., Kalamazoo Co., Mich., June 9, 1956 (R. L. Fischer, on Crataegus) [Univ. Mich.]. Paratypes: MICHIGAN: 2 MM, topotypical (Fischer, on Spirea vanhouteii); 6 MM, Topotypical (R. W. Hodges); 1 M, Lake Co., April 17, 1955 (R. W. Hodges); 1 M, Branch Co., June 1, 1941 (R. R. Dreisbach). WISCONSIN: 1 M, Boscobel, June 14, 1955 (R. W. Hodges). ONTARIO: 1 M, Pelee Is., June 27, (R. C. Osburn). OHIO: 5 MM, Miami Co., May 26 (C. H. Kennedy); 1 M Georgesville, May 31, 1925 (O. Cartwright); 1 M, Champaigne Co. 7 June, 1931 (D. Murray); MINNESOTA: 9 MM, Houston CO., May 21, 1938; 1 M, May 29, 1939 (H. E. Milliron); 1 M, Houston Co., May 21, 1938; 1 M, May 29, 1939 (C. E. Mickel); 2 MM, Houston Co., May 23, 1936 (Sterling Brackett); 1 M, Pine Co., May 25, 1941 (A. W. Buzicky); 1 M, John Latsch State Park, S. Minneiska, May 19 (A. T. Rozyck).
These paratypes are located in the University of Michigan, the University of Minnesota, Ohio State University, the collection of R. R. Dreisbach, and in the author's collection.
Described using the synonymous name: Andrena beutenmuelleri Viereck
FEMALE. — Length 12 mm.; clypeus only slightly convex, projecting about one-half below suborbital line, rather dull, quite closely and finely punctate except in mid line where punctures are more sparse, but without a distinct, median, impunctate line; facial foveae broad above, occupying most of area between eyes and ocelli, covered with pale ochraceous tomentum; space between margin of vertex and lateral ocelli slightly shorter than distance between ocelli; cheeks broader than eyes, rounded posteriorly, rather dull, very minutely and rather closely punctate; malar space very short; basal segment of flagellum subequal to 2nd and 3rd combined; process of labrum semicircular, about twice as broad as the median length; pubescence of head whitish, becoming ochraceous on vertex and on cheeks above, bright ochraceous on dorsum of thorax, becoming whitish on pleura, ochraceous on basal leg segments, becoming more fulvous on the more apical segments; thoracic integument rather dull but not densely tessellate, punctures of scutum shallow, rather close and fine, except near middle posteriorly where they are rather sparse; sparse on each side of scutellum, otherwise close and fine; pleura more densely tessellate, punctures shallow, fine, well separated in general, but becoming quite close below; enclosure of propodeum dull, tessellate, with some rather distinct basal striations; propodeal corbicula pale ochraceous, well developed but rather short, without a distinct anterior fringe, trochanteral floccus well developed, dense, whitish; tibial scopa dense, hairs simple, relatively elongate, more fulvous in color; basitarsi slightly narrower than their respective tibiae; 2nd submarginal cell slightly shorter than 3rd, receiving 1st recurrent near middle; abdominal terga somewhat shining, apical depressed areas distinct, occupying medially somewhat more than one-third length of the disc, minutely and rather sparsely punctate, punctures of remainder of discs uniformly fine and close but deep and distinct, discal pubescence extremely short, subappressed, white, fasciae not developed, tergum 5 with a rather dense, apical, pale fulvous fimbria.
DISTRIBUTION. — North Carolina, Ohio, Michigan and Minnesota; May and June.
FLOWER RECORD-Prunus angustifolia.