Reprinted with permission from: Mitchell, T.B. 1962 Bees of the Eastern United States. North Carolina Agricultural Experiment Station Technical Bulletin No. 152.|
FEMALE—Length 16-19 mm., breadth of abdomen 8-9 mm.; black, the tarsi piceous, tegulae brownish-testaceous, wings rather lightly infuscated, veins testaceous to blackish; face and cheeks largely black pubescent, but with erect, rather copious, yellowish pubescence between and above the antennae and on vertex; pubescence of thorax long and copious, pale yellowish in large part, but venter and posterior half of scutum largely black pubescent; legs with short, largely black pubescence; abdominal terga 1 and 2 with dense black pubescence, 3 and 4 yellow pubescent laterally but black medially, 5 largely black, but with some elongate, yellowish hairs at each extreme side, tergum 6 nearly bare; clypeus quite coarsely, closely and deeply punctate laterally, more finely so along upper margin, median apical area shining, with very minute and sparse punctures; labrum slightly excavated medially, basal area on each side triangularly produced, the projecting lip beyond this medially with a slightly elevated margin, the apical margin rather broadly rounded and considerably depressed; apex of mandible with a very slight, median notch, outer surface shining, with only extremely minute, scattered and obscure punctures evident; malar space shining, very irregularly and minutely punctate, median length about two-thirds basal width of mandible, and about one-third length of eye; lateral ocelli subequally distant from eyes and each other, distance to margin of vertex about twice as great; scape slightly more than half the length of the flagellum, segments 1 and 3 of flagellum about equal, segment 2 considerably shorter and slightly broader than long; sternum 6 shining, rather broadly rounded apically, strongly swollen on each side medially, with a quite dense, apical fringe of very short, brownish hairs.
MALE—Length 13-16 mm., breadth of abdomen 4-5.5 mm.; black, apical tarsal segments and spurs more piceous; tegulae brownish-testaceous; wings uniformly but lightly infuscated, veins testaceous to piceous; vertex with a median patch of elongate, yellow pubescence and a small amount of yellow just above antennae medially, head otherwise with copious and elongate, black pubescence; posterior half of scutum black pubescent, with a small amount of black on scutellum medially, the venter of thorax and lateral margins of propodeum black in part, otherwise pleura, scutum anteriorly, scutellum posteriorly and posterior face of propodeum with elongate, copious, yellow pubescence; legs black pubescent basally, becoming somewhat paler on the tarsal segments, the posterior fringes of sparse, elongate, pale hairs; abdominal terga 1-4 with copious, rather elongate, yellowish pubescence, 5-7 with black, a small amount of yellow on 6 laterally; clypeus finely, closely and deeply punctate in general, only the apical margin narrowly shining and impunctate medially; labrum shining, punctures minute, apical margin broadly subtruncate, only slightly depressed, with a transverse fringe of short, erect, black hairs; mandibles short and slender, distinctly bidentate apically, outer surface quite densely pubescent, lower margin with a fringe of elongate, more or less curved, fuscous hairs; malar space shining, with only very minute, scattered punctures, median length somewhat less than basal width of mandibles about one-fifth length of eye; lateral ocelli subequally distant from eyes and each other, distance to margin of vertex only slightly greater; punctures of face very fine and densely crowded, vertex medially with densely crowded but rather fine striate punctures medially, lateral punctures close but more rounded, area adjacent to each lateral ocellus polished and impunctate; scutum with a narrow, median area posteriorly where the surface is shining and sparsely punctate, punctures otherwise quite uniformly close on scutum, scutellum and pleura; sterna 7 and 8 and genital armature similar to variabilis (fig. 134).
DISTRIBUTION—Although widespread in Canada and the Northern United States, this species has been rare in collections received for study. Specimens have been identified only from New Brunswick and New York, May to August.
HOST — Plath (1934), quoting Sladen. gives Bombus flavifrons as the host of insularis. Since the ranges of these two species do not entirely coincide, it seems evident that it will select some other species of Bombus as well.