Reprinted with permission of the American Entomological Society from:
LaBerge, W. E. 1973. A revision of the bees of the genus Andrena of the Western Hemisphere. Part VI. Subgenus Trachandrena. Transactions of the American Entomological Society 99: 235-371.
Please report text errors to: leah at discoverlife dot org.
This is an abundant, nondescript bee occurring across the United States and southern Canada. The female can be readily distinguished from A. sigmundi females by the shorter, usually more densely punctate, second tergal apical area, the straight or smoothly curved posterior hind tibial spur and usually being without a distinct clypeal median impunctate line. The male of forbesii can be readily separated from most species of Trachandrena by the shiny black flagella and from that of sigmundi by the sixth sternum being deeply emarginate medially and by the hind tibial spur being straight as in the female.
FEMALE. MEASUREMENTS AND RATIOS. — N = 20; length, 8-11 mm; width 2.5-3.5 mm; wing length, M = 3.88 ± 0.200 mm; FL/FW, M = 1.09 ± 0.007; FOVL/FOVW, M = 3.73 ± 0.079.
INTEGUMENTAL COLOR. — Black except as follows: mandible with apical third to one-half rufescent; flagellar segments 3-10 dark red to brown below; wing membranes hyaline, slightly infumate apically, veins red to reddish-brown, pterostigma usually red; tegulae rufescent; distitarsi dark brown to red, basitarsi and hind tibiae occasionally red, usually brown; tibial spurs testaceous.
STRUCTURE. — Antennal scape length equal to first three and two-thirds flagellar segments or slightly more (less than first four segments); flagellar segment 1 slightly shorter than segments 2 plus 3, segment 2 subequal to 3 and each shorter than 4; segments 2 and 3 quadrate, 4-10 longer than broad. Eyes each four times as long as broad or slightly less, inner margins parallel. Malar space, mandible and galea as in sigmundi. Maxillary palpus as in sigmundi but segmental ratio about as 1.0:1.0:0.7:0.8:0.7:0.7. Labial palpus as in sigmundi but ratio about as 1.0:0.6:0.5:0.6. Labral process and labrum as in sigmundi but process entire and labrum apical to process with several weak, indistinct cristae crossing shallow transverse sulcus. Clypeus as in sigmundi but without longitudinal impunctate line or this reduced to a short, subapical, sparsely punctate area. Supraclypeal and genal areas as in sigmundi. Vertex, face above antennal fossae and facial foveae as in sigmundi.
Pronotum as in sigmundi but shinier especially dorsally. Thoracic sculpturing as in sigmundi but propodeum with dorsal enclosure with rugae lateral to median longitudinal ruga often irregular. Front femora with base rounded. Posterior hind tibial spur straight or smoothly curved. Wing venation as in sigmundi.
Metasomal tergum 1 with punctures as in sigmundi but usually more crowded, apical area with only apical fifth or less impunctate. Tergum 2 with apical area equal in length medially to basal area or very slightly shorter (usually shorter), punctures of basal and apical areas of same size and distribution, crowded, separated largely by half a puncture width or less, surface shiny. Terga 3 and 4 similar but punctures may be slightly sparser. Pygidial plate V-shaped with rounded apex, internal raised triangular area sharply V-shaped. Sterna as in sigmundi.
VESTITURE. — Generally as in sigmundi except as follows: terga 5 and 6 with hairs pale ochraceous to white; terga 2 and 3 usually with only a trace of apical pale pubescent bands present at extreme sides but western specimens usually with pale bands conspicuous but interrupted medially; tergum 4 with broadly interrupted apical pale pubescent band in most specimens but band often complete especially in western specimens.
MALE. MEASUREMENTS AND RATIOS. — N = 20; length, 7.5-10.0 mm; width, 2-3 mm; wing length, M = 3.50 ± 0.148 mm; FL/FW, M = 1.14 ± 0.008; FS1/FS2, M = 0.64 ± 0.13.
INTEGUMENTAL COLOR. — Black with same exceptions as in female but flagellar segments 2-11 reddish-brown below and wing membranes less infumate.
STRUCTURE. — Antennal length and scape length as in sigmundi; first flagellar segment much shorter than second, segment 2 usually one and one-third times as long as segment 1 or longer and slightly shorter than segment 3; segment 2 as long as broad or slightly longer, segments 3-11 at least one and one-half times as long as broad; flagellum shiny. Eyes as in sigmundi. Malar space, mandible, galea as in female. Maxillary palpus as in female but segmental ratio about as 1.0:1.0:0.9:0.9:0.9:0.9. Labial palpus as in female. Labral process as in sigmundi. Supraclypeal area, face above antennal fossae and vertex as in female. Genal area as in sigmundi.
Thoracic structure and sculpturing as in sigmundi but propodeum with dorsal enclosure with rugae often irregular. Posterior hind tibial spur smoothly curved or straight. Wing venation as in sigmundi.
Metasomal terga sculptured as in female but punctures often slightly sparser but never as sparse as in sigmundi and tergum 2 with apical area punctures of same size and distribution as basal area punctures. Tergum 2 with apical area with median length equal to about one-half of basal area length or slightly less. Sterna 2-5 sculptured as in sigmundi. Sternum 6 with apical margin with broadly V-shaped emargination. Terminalia as in sigmundi but see figures 24-25.
VESTITURE. — Generally as in sigmundi but slightly paler especially on vertex and thoracic dorsum.
GEOGRAPHICAL VARIATION. — Western populations of A. forbesii have a relatively high (near 50%) proportion of specimens with the tarsi and hind tibiae red or orange in color. At least one specimen from the east (New Hampshire) is also so marked. These specimens would bear the name lincolni if considered to be a separate species. Rarely the red-legged western specimens (only two out of nearly 100) have the facial fovea rather broad in the lower half, although long and parallel-sided. This indicates that the red-legged condition may be due to hybridization and introgression on a small scale with A. hippotes Robertson. Sculptural characters, however, separate these two species readily.
Western specimens also have more regularly well-formed apical pale pubescent bands on terga 2-4 in females and terga 2-5 in males.
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 rather strongly convex projecting about one-third below suborbital line, smooth and shining between irregular, close, deep and rather coarse punctures, without a distinct median impunctate line; facial foveae rather broad above, occupying about two-thirds of area between eyes and ocelli, quite strongly constricted below, the constricted portion about half the width of the broad upper portion, covered with pale ochraceous tomentum; space between margin of vertex and lateral ocelli subequal to their diameter; cheeks subequal to eyes in width, rather dull, closely, deeply and rather finely punctate, punctures quite close even on lateral areas of vertex; malar space very short; basal segment of flagellum slightly shorter than 2nd and 3rd combined; process of labrum about twice as broad basally as long, subtriangular, with rather broadly truncate apex, pubescence of head, thorax and legs pale ochraceous, somewhat brighter ochraceous on dorsum of thorax and becoming somewhat fuscous on the more apical leg joints; punctures of scutum quite coarse, close and deep anteriorly, becoming quite sparse near center posteriorly where the surface is shining, those on scutellum close, somewhat irregular, surface shining; pleura dull, rather coarsely rugose above, becoming more tessellate posteriorly; dorsal area of propodeum oblique, triangle quite evenly and rather coarsely striate; propodeal corbicula rather poorly developed, without a distinct anterior fringe, pale ochraceous; trochanteral floccus short and poorly developed, ochraceous, hind tibiae rather slender, apex only slightly broader than basitarsi, scopa rather dense, composed of rather short, simple hairs, pale ochraceous, becoming fuscous at extreme base; front and mid basitarsi only very slightly narrower than their respective tibiae; 2nd submarginal cell considerably shorter than 3rd, receiving 1st recurrent near middle; abdominal terga smooth, shining, closely, deeply and rather finely punctate, apical impressed areas rather shallow, occupying medially somewhat over one-third length of disc, becoming narrowly reddish-hyaline along rims, discal pubescence very short, thin, erect, entirely pale, forming rather dense, pale ochraceous, apical fasciae on terga 2-4, that on tergum 2 widely interrupted medially, tergum 5 with a brownish, apical fimbria.
MALE. — Length 8 mm.; face very slightly longer than broad; clypeus rather strongly convex, projecting nearly one-half below suborbital line, closely, deeply and rather coarsely punctate, punctures almost crowded, but narrow interspaces shining; space between margin of vertex and lateral ocelli subequal to their diameter; cheeks subequal to eyes in width, dull, densely tessellate, punctures exceedingly obscure; malar space very short; basal segment of flagellum very short, about as long as its apical width, distinctly shorter than 2nd and following segments; process of labrum short and quite broad, subtriangular, apex rather broadly truncate; mandibles rather short, with a distinct, inner, subapical tooth, overlapping very slightly; pubescence of head, thorax and legs entirely whitish-ochraceous; scutum rather dull, closely and rather coarsely punctate anteriorly, punctures becoming quite sparse near middle posteriorly, those on scutellum of about equal size, somewhat sparse on each side, surface more shining; pleura dull, densely tessellate, obscurely and shallowly rugose; dorsal area of propodeum oblique, triangle finely and irregularly striate; all basitarsi slender and elongate, considerably narrower than their respective tibiae; 2nd submarginal cell considerably shorter than 3rd, receiving 1st recurrent near middle; abdominal terga somewhat shining between close, deep, fine punctures, apical impressed areas quite shallow, occupying medially about one-third length of discs, becoming narrowly yellowish-hyaline along rims, discal pubescence short, thin, erect, entirely pale, terga 2-4 with whitish apical fasciae evident at least toward sides, rather widely interrupted medially; apical portion of sternum 8 very slender and elongate, apex slightly expanded, subtruncate, clothed beneath with rather long, pale pubescence; penis valves slender apically, slightly expanded basally, sides quite strongly excavated, gonocoxites broadly expanded apically, forming triangular lobes, which are markedly concave on dorsal surface, gonocoxal lobes strongly produced, slender, acute, slightly curved, attaining the apical lobes (similar to hippotes, fig. 37).
DISTRIBUTION. — Colorado and Nebraska to the New England states and Nova Scotia, south to Georgia; March to July.
FLOWER RECORDS. — Amelanchier, Aronia, Brassica, Cornus, Crataegus, Ilex, Malus, Prunus, Pyracantha, Rubus, Salix and Viburnum. Recorded by Robertson (1929) on Antennaria, Capsella, Claytonia, Erigenia, Fragaria, Heracleum, Isopyrum, Polytaenia, Ptelea, Rhus, Sassafras, Stellaria, Zanthoxylum and Zizia.
Described using the synonymous name: Andrena pyracanthae Mitchell
FEMALE. — Length 10 mm.; face slightly longer than distance between eyes above; eyes subparallel; foveae abruptly and narrowly constricted below, this area separated from eye margin by a nearly equal space; vertex rather narrow, lateral ocelli separated from its hind margin by little more than their diameter; cheeks equal to eyes in width; clypeus protruding nearly one-half below suborbital line, smooth and shining between deep, distinct, rather coarse and close, uniformly distributed punctures; punctures of face below ocelli deep and distinct, well separated but not sparse, surface somewhat shining, those on vertex somewhat closer and finer, becoming very fine and quite close on cheeks; malar space extremely short; process of labrum broadly triangular, with truncate apex, length less than half its basal width; basal segment of flagellum not quite equaling 2nd and 3rd segments combined. median segments somewhat longer than broad; pubescence of head and thorax entirely pale, more whitish below, becoming yellowish above, erect and rather thin, more copious along outer margins of dorsum of thorax; scutum and scutellum somewhat shining, punctures deep and distinct, rather close but not crowded anteriorly, becoming rather sparse posteriorly on scutum, those on scutellum quite similar; pleura dull, densely and finely rugose anteriorly, becoming rather smooth and obscurely punctate posteriorly; dorsal area of propodeum rather finely striate, lateral areas finely rugose, propodeal corbicula rather short but dense, with a few scattered hairs on inner surface; trochanteral floccus rather well developed; legs dark, basitarsi quite narrow, pubescence entirely pale, hind tibiae rather slender, scopa of elongate white hairs; spurs pale testaceous; wings lightly infuscated, veins and stigma ferruginous, 2nd submarginal cell short, receiving 1st recurrent near middle; tegulae piceous, becoming somewhat yellowish-hyaline posteriorly toward outer margin; abdominal terga shining between deep, distinct, close and rather coarse punctures, terga 2-4 impressed for about half their median length, becoming very narrowly reddened along apical rims, apical fasciae very poorly developed, if at all evident, apical fimbria whitish.
TYPES. — Holotype: Female, Raleigh, N. C., April 20, 1957 (Mitchell, on Pyracantha). Paratypes: 2 FF, Whiteside Mt., N. C., June 6, 1957 (on Rubus); 2 FF, Wake Co., N. C., April 2, 1955 (on Crataegus and Pyracantha) (both Mitchell); 1 F, Raleigh, N. C., April 30, 1955 (D. A. Becker) [all authors' coll.].