Reprinted with permission from: Mitchell, T.B. 1962 Bees of the Eastern United States. North Carolina Agricultural Experiment Station Technical Bulletin No. 152.
Bombus nevadensis auricomus (Robertson)
Bombus auricomus Robertson, 1903. Amer. Ent. Soc. Trans. 29, p. 176.
Bombus auricomus Frison, 1917. Eat. Soc. Amer. Ann. 10, pp. 277-286. (biology)
Bombus auricomus Frison, 1918. Eat. Soc. Amer. Ann. 11, pp. 43-48. (biology)
Bombus auricomus Robertson, 1929. Flowers and Insects, Lancaster, Pa., Science Press. (flower records)
Bombus auricomus Plath, 1934. Bumblebees and their ways, New York, Macmillan, p. 153. (biology)
Auricornus Group, Milliron, 1961. Kans. Eat. Soc. Jour. 34, p. 56.
QUEEN—Length 20-25 mm., breadth of abdomen 9.5-11 mm.; black, legs reddish-piceous, apical tarsal segments somewhat more brownish, spurs and tegulae reddish-piceous; wings quite deeply infuscated basally, becoming somewhat paler apically, veins testaceous to black; pubescence rather short but quite dense, largely black on head, but vertex with a transverse band of yellow pubescence, posterior margin fringed with black; pubescence yellow on pronotum, tubercles and anterior margin of scutum, otherwise blackish or fuscous on thorax, largely black on legs, corbicular fringe fuscous or black, hind basitarsi thickly clothed with more reddish pubescence beneath, the more apical tarsal segments of all thinly clothed with very short pale tomentum; propodeum posteriorly with a thin covering of short, subappressed, golden tomenturn, and with erect, darker hairs; abdominal terga 2 and 3 with a dense covering of short, yellow pubescence, terga 1 and 4-6 entirely black; clypeus shining, with rather sparse, very minute punctures and scattered, coarser punctures, more numerous laterally and above; labrum broadly rounded, with a basal ridge which is slightly interrupted medially, with a dense median tuft of more or less erect, brownish hairs, apical margin considerably depressed; apex of mandibles with a broad, rounded, lower margin or cutting edge and a pair of inner, nearly apical, acute teeth (in unworn specimens), the outer face toward the base rather dull, with exceedingly minute, vague and close punctures; malar space smooth and shining, hardly punctate, its length somewhat greater than basal width of mandible; eye about three and one-half times that of malar space; ocelli distinctly below supraorbital line, lateral ocelli slightly nearer eyes than to each other, and nearer each other than to margin of vertex; total length of flagellum about twice that of scape, basal segment about equal to segments 2 and 3 combined; face finely and closely punctate, becoming shining and nearly impunctate adjacent to lateral ocelli; vertex densely and finely punctate medially, becoming shining and rather sparsely punctate laterally; scutum with a limited median posterior area that is shining and impunctate; hind basitarsus parallel- sided, width somewhat less than half the length; tergum 6 with a slight, median, apical ridge.
WORKER—Length 18-20 mm., breadth of abdomen 8-9 mm.; resembles queen except in size.
MALE—Length 17-20 mm., breadth of abdomen 8-9 mm.; black, apical tarsal segments somewhat more brownish-testaceous, mid and hind spurs piceous and tegulae reddish-piceous; wings rather uniformly and deeply infuscated, veins testaceous to piceous; pibescence short but quite copious and dense, pale yellowish on vertex and occiput, with some intermixed yellowish and black hairs on face medially, blackish on cheeks and lower part of face; pubescence yellowish on scutum, scutellum and pleura, with a slight tawny tinge, scutum posteriorly with an intermixture of short, more fuscous hairs, that on scutellum more elongate and conspicuous on each side of a narrow, median, nearly bare line; pubescence fuscous on propodeuna and venter along mid line; legs fuscous or blackish pubescent in general, mid and hind basitarsi with fringes of rather elongate, dark hairs, the more apical segments with very fine, more or less appressed, pale tomentum; abdominal terga 1-3 entirely yellow pubescent, this with a slightly reddish tinge at certain angles, the hairs quite short but dense, 4-7 entirely black, the hairs more elongate and erect except on 7 medially; eyes large and bulging, strongly converging above, lateral ocelli nearly contiguous with the inner margin, located about at mid-point between margin of vertex and antennae; clypeus finely and closely punctate in large part, apical margin somewhat more shining and more minutely and vaguely punctate; labrum rather broadly rounded or sub- truncate apically, shining laterally, more densely and finely punctate medially; mandibles quite short and slender, bidentate apically, lower tooth rounded, upper tooth more acute, outer surface densely yellowish tomentose, lower margin with a fringe of elongate, dark hairs; nialar space shining and nearly impunctate, short, its length only slightly more than half the basal width of mandibles; total length of flagellum somewhat more than twice length of scape, basal segment subequal in length to 2 and 3 combined; margins of hind basitarsi nearly parallel, the length somewhat more than twice the breadth; sterna 7 and 8 and genital armature as in nevadensis (fig. 130).
DISTRIBUTION — Minnesota to New York, south to Georgia, May to September.
FLOWER RECORDS—Ceanot hue, Hypericum, Malus and Rubus.
Milliron (1961) finds that auricornus is only subspecifically different from nevadensis, and states in correspondence that all intergradations between the two forms are to be found. This is the more eastern form, while typical neva4ensis occurs only sparingly east of the Mississippi.
Bombus nevadensis nevadensis
Cresson
Bombus nevadensis Cresson, 1874. Amer. Ent. Soc., Trans. 5, p. 102. 2 .
Bombus improbus Cresson, 1878. Acad. Nat. Sd. Phila. Proc., p. 186. .
QUEEN—Pubescence of head entirely black, largely yellow on pronotum, scutum and scutellum, with a few black hairs in center of scutum, entirely black on pleura, propodeum and legs; abdominal terga 2 and 3 yellow, the basal tergum black at base, but yellow along apical margin of disc, 4-6 entirely black.
WORKER—Pattern of pubescence similar to that of queen.
MALE—Legs with posterior fringes of long, yellowish hairs, and tarsi with very short, yellowish pubescence; abdominal terga 1-3 and 6-7 with pubescence entirely yellow, that on 4-5 largely black, but becoming more or less yellowish laterally and apically.
DISTRIBUTION — Western United States, from Pacific coast to Illinois.
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