Reprinted with permission of the American Entomological Society from:
LaBerge, W. E., Ribble, D. W. 1972. A revision of the bees of the genus Andrena of the Western Hemisphere. Part V: Gonandrena, Geissandrena, Parandrena, Pelicandrena. Transactions of the American Entomological Society 98: 271-358.
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Described under the synonymous name: Andrena nigrifrons
Andrena nigrifrons is the most common of the Gonandrena and like the previous species is an inhabitant of our eastern deciduous forests. The female of nigrifrons is like fragilis in the hairy thoracic dorsum and the rounded mesepisternum but differs from fragilis in the smaller, trapezoidal labral process. The male of nigrifrons is like that of integra and unlike that of fragilis in the dark flagellum, the more shallowly emarginate clypeus and the well-formed sternal fimbriae. The male differs from that of integra by the more distinctly punctate clypeus and metasomal terga.
As in integra, nigrifrons has an occasional specimen with two submarginal cells in one or both wings (including the holotype). In the male sex this amounts to 10% with one wing and 16% with both wings with two submarginal cells instead of three, but in the females only about 5% of the specimens show such aberrations.
FEMALE. MEASUREMENTS AND RATIOS: N = 20; length, 8-10 mm; width, 2.5-3.0 mm; wing length, M = 3.56 ± 0.129 mm; FL/FW, M = 1.02 ± 0.004; FOVL/FOVW, M = 5.16 ± 0.098.
INTEGUMENTAL COLOR. — As in fragilis except flagella dark reddish-brown to black and tergal apical areas piceous to slightly translucent.
STRUCTURE. — Antennal scape length equal to first four flagellar segments; flagellar segments as in fragilis. Eyes each about three and one-half times as long as broad or slightly longer, inner margins parallel. Mandible and galea as in fragilis. Labial palpus as in fragilis but ratio about as 1.0:0.6; 0.4:0.5. Maxillary palpus as in fragilis. Labral process flat, trapezoidal, often slightly depressed medially; labrum below process not sulcate or only weakly so, shiny. Clypeus as in fragilis but impunctate midline often broader. Supraclypeal area, face above antennal fossae and vertex as in fragilis. Genal area as in fragilis but posterior carina usually incomplete below and weak, occasionally absent. Facial fovea as in fragilis but slightly narrower.
Pronotum as in integra. Thoracic form and sculpture as in fragilis. Wing venation as in integra.
Metasomal terga and sterna sculptured as in fragilis but terga 2-4 often slightly more shagreened basally. Pygidial plate as in fragilis.
VESTITURE. — As in fragilis but scopal hairs weakly plumose anteriorly, basitibial plate with dark brown hairs (and scopal hairs below plate often brown), and terga 2 and 3 always with apical pale fasciae interrupted medially.
MALE. MEASUREMENTS AND RATIOS: N = 20; length, 6.5-9.0 mm; width, 1.5-2.5 mm; wing length, M = 3.05 ± 0.196 mm; FL/FW, M = 1.05 ± 0.005; FS1/FS2, M = 1.90 ± 0.029.
INTEGUMENTAL COLOR. — As in fragilis except flagellum dark brown to black below.
STRUCTURE. — Antenna as in fragilis except first flagellar segment distinctly shorter than segments 2 plus 3 and segment 3 about as long as 4. Eyes each about three times as long as broad, inner margins parallel. Mandible and galea as in fragilis. Labial palpus as in fragilis but ratio about as 1.0:0.6:0.5:0.6. Maxillary palpus as in fragilis but ratio about as 0.8:1.0: 0.6:0.6:0.5:0.6. Labrum as in fragilis. Clypeus as in fragilis, free apical margin along shallowly emarginate, surface of clypeus reticularly shagreened but clypeus always at least moderately shiny. Supraclypeal area, face above antennal fossae and vertex as in fragilis. Genal area as in fragilis but posterior carina usually absent in lower half and less distinct above.
Thoracic form and sculpturing as in fragilis. Wing venation as in integra but second submarginal cell (when three are present) usually narrower; one or both wings with only two submarginal cells in about 25% of specimens.
Metasomal sculpturing as in female. Sternum 6 as in fragilis. Terminalia as in fragilis but penis valves shorter, not nearly as long as apical process of gonocoxite, with ventral lamellae broader than dorsal lamellae when viewed from above; sternum 8 with apex scarcely if any broader than neck, truncate (Figs. 20-21).
VESTITURE. — As in fragilis except that sternum 2 as well as sterna 3-5 with well-formed, apical fimbriae of long hairs which are slightly curled near tips.
REMARKS. — The form named monroensis by T. B. Mitchell (1960) consists of several females from localities scattered throughout the range of nigrifrons. These females are slightly larger, tend to have a slightly more punctate clypeus (except along midline) and shinier abdomen. None of these characters are definitive and each grades into the usual condition in nigrifrons. No male can be associated with such females. Therefore, we conclude that these females represent no more than an extreme size variation within the species nigrifrons.
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 9 mm.; clypeus broadly convex, projecting nearly one-half below suborbital line, rather dull, finely punctate, punctures well separated medially, becoming rather close at extreme sides, with an indefinite, median, impunctate line; facial foveae narrow, occupying above hardly half of space between eyes and ocelli (as in integra, fig. 49), covered with pale ochraceous tomentum; space between margin of vertex and lateral ocelli subequal to their diameter; cheeks very slightly broader than eyes, rounded posteriorly, upper part subcarinate posteriorly, rather dull, punctures exceedingly minute and rather close; malar space extremely short; basal segment of flagellum subequal to 2nd and 3rd combined; process of labrum nearly as long as broad, narrowed apically to the narrowly truncate apex; mandibles somewhat dilated beneath toward base; pubescence of head, thorax and legs whitish, faintly tinged with yellowish above and on legs apically; thoracic integument dull, punctures of scutum rather shallow, fine and well separated, those on scutellum more minute, scattered and irregular, surface shining; pleura roughened or finely subrugose above, punctures otherwise very obscure; dorsal area of propodeum nearly horizontal, triangle finely rugoso-striate; propodeal corbicula rather poorly developed, thin, pale ochraceous, without an anterior fringe; trochanteral floccus well developed, whitish; hind tibiae very slender, only very slightly broader than basitarsi, scopa rather dense, of somewhat elongated simple hairs, entirely pale ochraceous; front and middle basitarsi slightly narrower than their respective tibiae; 2nd submarginal cell considerably shorter than 3rd, receiving 1st recurrent about one-third from apex; abdominal terga smooth and shining, punctures very fine but rather distinct, very sparse on basal tergum, somewhat closer on the others, quite close laterally, becoming rather widely separated medially, apical impressed areas quite shallow, rather narrow, becoming narrowly yellowish-hyaline along rims, discal pubescence extremely short and sparse, entirely pale, terga 2-4 with thin, whitish, apical fasciae, rather widely interrupted on tergum 2 medially, tergum 5 with a brownish-ochraceous, apical fimbria.
DISTRIBUTION. — Ontario and the New England states, south to North Carolina, and west to Kansas and Texas; June and July.
FLOWER RECORDS. — Cornus asperifolia and Viburnum.
The type series of 19 FF, now in the collection of the Illinois Natural History Survey, has been seen and found to be composed of two distinct species. Eight of the specimens, having a large quadrate labral process, are without doubt Andrena fragilis Smith. The remaining 11 specimens are identical with Andrena barbarica Viereck. The lectotype specimen is one of the latter, and can justifiably be assumed to represent the true platyparia. The description (Robertson, 1895) is of little help in deciding which of these two to select, as the distinctive feature separating them is treated as a variation, and both conditions are given. Thus it seems that the name platyparia should be resurrected, and barbarica becomes a synonym of it.
Described under the synonymous name: Andrena monroensis
FEMALE — Length 10 mm.; face nearly as long as distance between eyes above; eyes about parallel; foveae narrow, occupying no more than half of space between eyes and ocelli above (slightly narrower than in robertsonii, fig. 49), and terminating about at level of antennae; lateral ocelli separated from margin of vertex by about their own diameter; cheeks considerably broader than eyes, subcarinate above; clypeus moderately convex, protruding about one-half below suborbital line, somewhat shining, with a median impunctate line, punctures on each side rather deep and distinct, well separated but becoming quite close at extreme lateral angles; face below ocelli rugoso-striate, vertex shining, with a few obscure irregularities medially and some rather fine and close punctures at extreme sides, cheeks becoming quite smooth but rather dull, punctures minute, rather close toward margin of eye, but obscure throughout; malar space hardly evident; process of labrum subtriangular with a rather narrowly subtruncate apex, length considerably more than half basal width; basal segment of flagellum fully equal to 2nd and 3rd combined, these considerably shorter than broad, the more apical segments slightly longer than broad; pubescence of head and thorax rather thin, erect, whitish on face and cheeks and on thorax laterally and beneath, becoming somewhat yellowish on vertex and dorsum of thorax; scutum rather dull anteriorly and laterally, punctures rather shallow and fine but distinct, well separated even anteriorly, becoming rather sparse near center posteriorly, scutellum polished, with scattered, minute but quite distinct punctures; pleura dull but rather smooth, tessellate, becoming almost rugose anteriorly; dorsal area of propodeum finely rugoso-striate, lateral areas becoming very finely rugose, propodeal corbicula rather short but distinct, with few if any interior hairs and without an anterior fringe; trochanteral floccus complete, quite elongate; legs blackish, quite slender, basitarsi narrow and parallel-sided, hind tibiae quite slender to tip, scopa of elongate whitish hairs, spurs pale testaceous; wings subhyaline, very faintly clouded toward apex, veins pale testaceous, stigma more brownish, 2nd submarginal cell hardly half length of 3rd, receiving 1st recurrent near its apex; tegulae piceous basally, becoming yellowish-hyaline posteriorly; abdominal terga polished, punctures very fine but distinct, well separated, evenly distributed, 2nd and 3rd segments rather narrowly impressed apically, becoming very narrowly hyaline along apical rim, segments 2-4 with narrow, whitish but quite dense, apical fasciae, these interrupted on 2nd and 3rd, apical fimbria pale brownish.
TYPES - Holotype: Female, Monroe Co., Mich., June 23, 1940 (R. R. Dreisbach) [Dreisbach]. Paratype: 1 F, Grand Rapids, Mich., June 25, 1937 [Univ. Mich.]