SQUARE- OR LONG-CHEEKED BEES WITH A ROUNDED ANGLE ON THE MIDLEG

BOMBUS VOSNESENSKII RADOSZKOWSKI, 1862

VOSNESENSKY BUMBLE BEE

IDENTIFICATION

Western, medium tongue-length species. Most similar to B. caliginosus and B. vandykei (see also B. occidentalis, B. franklini, B. fervidus, B. insularis, and B. flavidus).

HAND CHARACTERS Body size medium (larger than B. caliginosus, B. vandykei): queen 18–21 mm (0.69–0.83 inch), worker 8–17 mm (0.33–0.65 inch). Hair short and even. Head length medium with the cheek (oculo-malar area) as long as broad (contrast B. occidentalis, B. franklini, B. fervidus), midleg basitarsus with the back far corner rounded, hindleg tibia outer surface flat without long hair but with long fringes at the sides, forming a pollen basket (corbicula). Hair of metasomal T3 black (contrast B. vandykei), T4 almost entirely yellow with just a few black hairs near the midline (contrast B. caliginosus, B. vandykei), S2–5 with black fringes at the back (contrast B. caliginosus) or very rarely with yellow at the sides. Male 10–15 mm (0.40–0.58 inch). Eye similar in size and shape to the eye of any female bumble bee. Antenna of medium length, flagellum 3× longer than the scape (contrast B. occidentalis, B. franklini, B. fervidus). Hair color pattern similar to the queen/worker, but metasomal T5 at the sides with yellow, rarely with yellow intermixed broadly on the upperside of the thorax at the back.

MICROSCOPIC CHARACTERS Queen/worker lower central area of the clypeus with many large pits or punctures (contrast B. caliginosus). Male genitalia with the penis-valve head sickle-shaped, the back-curved "sickle" long and very narrow, at least 3× longer than its breadth in the further half and less than half the breadth of the adjacent neck of the penis-valve head, the "sickle" scarcely flattened and about 2× broader than thick, almost spinelike (contrast B. caliginosus, B. vandykei), gonostylus longer than broad (contrast B. caliginosus, B. vandykei), the inner (medial) edge concave.

OCCURRENCE

RANGE AND STATUS Mediterranean CA and Mountain West of CA, OR, WA, southern BC and adjacent Desert West in CA. From sea level to above 2700 m. One of the most common species near the west coast.

HABITAT Open grassy areas, urban parks and gardens, chaparral and shrub areas, mountain meadows.

EXAMPLE FOOD PLANTSArctostaphylos, Ceanothus, Chrysothamnus, Cirsium, Eriogonum, Eschscholzia, Lupinus, Phacelia, Rhododendron, Ribes, Vicia, Ericameria, Clarkia, Grindelia.

BEHAVIOR Nests underground. Males patrol circuits in search of mates.

PARASITISM BY OTHER BEES Unknown.

BOMBUS CALIGINOSUS (FRISON, 1927)

OBSCURE BUMBLE BEE

IDENTIFICATION

Western coastal, medium long-tongued species. Most similar to B. vosnesenskii and B. vandykei (see also B. occidentalis, B. franklini, B. fervidus, B. insularis, and B. flavidus).

HAND CHARACTERS Body size small (smaller than B. vosnesenskii, larger than B. vandykei): queen 16–18 mm (0.62–0.71 inch), worker 11–13 mm (0.43–0.50 inch). Hair short but slightly shaggy and uneven. Head length medium with the cheek (oculo-malar area) very slightly longer than broad (contrast B. occidentalis, B. franklini, B. fervidus), midleg basitarsus with the back far corner rounded, hindleg tibia outer surface flat without long hair but with long fringes at the sides, forming a pollen basket (corbicula). Hair of metasomal T3 black (contrast B. vandykei), T4 yellow but with black at the front and often forming a triangle in the middle and narrowly interrupting the yellow along the midline (contrast B. vosnesenskii, B. vandykei), S4 or S3–4 usually with pale fringes at the sides at the back (contrast B. vosnesenskii) or very rarely nearly entirely black, S2 and S5 with black fringes. Male 11–13 mm (0.46–0.49 inch). Eye similar in size and shape to the eye of any female bumble bee. Antenna of medium length, flagellum 3× longer than the scape (contrast B. occidentalis, B. franklini, B. fervidus). Hair color pattern similar to the queen/ worker.

MICROSCOPIC CHARACTERS Queen/worker lower central area of the clypeus with only small and not large pits or punctures (contrast B. vosnesenskii). Male hair of the upperside of the thorax at the back (scutellum) with a few yellow hairs intermixed, metasomal T4 with some black hair at the front, T5 yellow at the sides and sometimes at the back. Antennal segment A3 long, length nearly 2× the maximum breadth, almost as long as antennal segment A5. Genitalia with the penis-valve head sickle-shaped, the back-curved "sickle" short and broad (contrast B. vosnesenskii) less than 2× longer than the breadth of the broadest part and similar in breadth to the adjacent neck of the penis-valve head, the "sickle" flattened and broadly rounded at the tip, gonostylus shorter than broad (contrast B. vosnesenskii), the inner (medial) edge nearly straight, the margin thin with a short indistinct parallel submarginal groove.

OCCURRENCE

RANGE AND STATUS Mediterranean CA and Pacific Coast from southern CA to southern BC, with scattered records from the east side of CA Central Valley. Uncommon.

HABITAT Open grassy coastal prairies and Coast Range meadows.

EXAMPLE FOOD PLANTSCeanothus, Cirsium, Clarkia, Keckiella, Lathyrus, Lotus, Lupinus, Rhododendron, Rubus, Trifolium, Vaccinium.

BEHAVIOR Nests underground, also nests aboveground in abandoned bird nests. Males patrol circuits in search of mates.

PARASITISM BY OTHER BEES Unknown.

BOMBUS VANDYKEI (FRISON, 1927)

VAN DYKE BUMBLE BEE (INCLUDING CASCADENSIS)

IDENTIFICATION

Western, medium long-tongued species. Most similar to B. vosnesenskii and B. caliginosus (see also B. occidentalis, B. franklini, B. fervidus, B. insularis, and B. flavidus). The extensively yellow female color pattern (unnecessarily redescribed with the name cascadensis, from WA, northern OR) is rare in collections compared to the darker female color patterns from southern OR, CA.

HAND CHARACTERS Body size small (smaller than B. vosnesenskii, B. caliginosus): queen 14–18 mm (0.56–0.72 inch), worker 10–14 mm (0.39–0.50 inch). Hair short but slightly shaggy and uneven. Head length medium with the cheek (oculo-malar area) longer than broad (contrast B. occidentalis, B. franklini), midleg basitarsus with the back far corner rounded, hindleg tibia outer surface flat without long hair but with long fringes at the sides, forming a pollen basket (corbicula). Hair of metasomal T3 yellow at least in the back half (contrast B. vosnesenskii, B. caliginosus) and usually with some black at the front and in the middle, T4 usually black but T1–2 and T4 may rarely have small yellow patches at the sides, S2–5 with pale fringes at the back. Male 10–13 mm (0.41–0.52 inch). Eye similar in size and shape to the eye of any female bumble bee. Antenna of medium length, flagellum 2.5–3× longer than the scape (contrast B. occidentalis, B. franklini, B. fervidus). Hair usually predominantly yellow (contrast B. vosnesenskii, B. caliginosus), upperside of the thorax between the wings with black intermixed in a narrow band, metasomal T3–4 usually yellow, without black intermixed, but rare dark males have yellow only on the upperside of the thorax at the front and on T2–3 with black behind the wings and on T1 (contrast some B. flavifrons).

MICROSCOPIC CHARACTERS Male antennal segment A3 long, length nearly 2× maximum breadth, almost as long as antennal segment A5. Genitalia with the penis valve sickle-shaped, the back-curved "sickle" short and broad (contrast B. vosnesenskii), about 2× longer than the breadth of the broadest part and similar in breadth to adjacent neck of the penis-valve head, the "sickle" flattened and broadly rounded at the tip, gonostylus shorter than broad (contrast B. vosnesenskii), the inner (medial) edge nearly straight, the margin thin with a short indistinct parallel submarginal groove.

OCCURRENCE

RANGE AND STATUS Mediterranean CA and Mountain West of CA, OR, WA, to southern BC. From the Transverse Ranges, mostly through the Sierra-Cascade Ranges and sparingly through the Coast Ranges. From sea level up to 2,200 m. Moderately common.

HABITAT Open grassy prairies and meadows.

EXAMPLE FOOD PLANTSCirsium, Clarkia, Collinsia, Delphinium, Eriodyction, Lupinus, Penstemon, Phacelia, Salvia, Stachys, Trifolium.

BEHAVIOR Nests underground. Males patrol circuits in search of mates.

PARASITISM BY OTHER BEES Unknown.

BOMBUS IMPATIENS CRESSON, 1863

COMMON EASTERN BUMBLE BEE

IDENTIFICATION

Eastern, medium-tongued species. Most similar to B. bimaculatus, B. perplexus, B. vagans, and B. sandersoni (see also B. citrinus, B. variabilis, B. griseocollis, and some B. rufocinctus).

HAND CHARACTERS Body size large: queen 21–23 mm (0.81–0.90 inch), worker 9–14 mm (0.34–0.56 inch). Hair short and even. Head length medium with the cheek (oculo-malar area) as long as broad or just shorter than broad (contrast B. griseocollis, B. rufocinctus), midleg basitarsus with the back far corner rounded, hindleg tibia outer surface flat without long hair but with long fringes at the sides, forming a pollen basket (corbicula). Hair of the face black or with a few yellow hairs intermixed, thorax predominantly yellow, the upperside with short black hairs intermixed diffusely in a large square between the wings, metasomal T1 yellow, T2 usually entirely black (contrast B. bimaculatus, B. perplexus, B. vagans, B. sandersoni), tail black. Rarely T2–3 with orange-red hair at the back, although this may be from damage at the pupal stage. Very rarely worker T2 with a few yellow hairs at the front near the middle. Body rather long and rectangular. Male 12–14 mm (0.48–0.54 inch). Eye similar in size and shape to the eye of any female bumble bee (contrast B. griseocollis, B. rufocinctus). Antenna of medium length, flagellum 3× longer than the scape. Hair color pattern similar to the queen/worker, but below the antenna a patch of yellow, and on the underside and on the legs and metasomal S2–6 many yellow hairs. Rarely T2 with a few yellow hairs at the front and in the middle, very rarely T4–5 with small patches of yellow at the sides.

MICROSCOPIC CHARACTERS Queen metasomal T6 near the tip flat or with a weak lengthwise ridge just before the tip (contrast B. perplexus). Male genitalia with the penis valve sickle-shaped, the back-curved "sickle" long and narrow, at least 3× longer than broad and less than half the breadth of the adjacent neck of the penis-valve head, the "sickle" scarcely flattened and about 2× broader than thick, almost spinelike, gonostylus with the inner (medial) edge concave.

OCCURRENCE

RANGE AND STATUS One of the most widespread and abundant species in the Eastern Temperate Forest region of the eastern US and adjacent southern Canada, as far west as the eastern Great Plains. Possibly expanding in range toward the northeast. Commonly used for pollination of greenhouse crops. Apparently naturalized from escapes in southern BC and perhaps elsewhere.

HABITAT Close to or within woodland, grassland, farmland, wetlands, urban parks and gardens.

EXAMPLE FOOD PLANTS"Aster", Cirsium, Eupatorium, Gelsemium, Impatiens, Malus, Pontederia, Rubus, Solidago, Trifolium.

BEHAVIOR Nests underground. Males patrol circuits in search of mates.

PARASITISM BY OTHER BEES Host to B. citrinus, confirmed breeding record.

BOMBUS BIMACULATUS CRESSON, 1863

TWO-SPOTTED BUMBLE BEE

IDENTIFICATION

Eastern, medium-tongued species. Most similar to B. impatiens, B. perplexus, B. vagans, and B. sandersoni (see also B. griseocollis, some B. rufocinctus, B. affinis, B. citrinus, and B. variabilis). The lightest and darkest female color patterns are rare.

HAND CHARACTERS Body size medium: queen 18–22 mm (0.71–0.85 inch), worker 10–16 mm (0.38–0.63 inch). Hair long and uneven (contrast B. impatiens, B. griseocollis). Head length medium with the cheek (oculo-malar area) just longer than broad (contrast B. griseocollis, B. rufocinctus), midleg basitarsus with the back far corner rounded, hindleg tibia outer surface flat without long hair but with long fringes at the sides, forming a pollen basket (corbicula). Hair of the face black or with only a few yellow hairs intermixed, upperside of thorax between the wings with a dense black spot always present although often with yellow hairs intermixed, only occasionally forming a black band between the wings, sides of the thorax yellow (contrast B. perplexus), metasomal T2 usually extensively black at least at the sides in front (contrast B. vagans, B. sandersoni), always with a small patch of yellow present in the front near the midline (contrast B. impatiens) but this varies in extent, although the back edge of the yellow usually forming a characteristic W shape (which may be similar in a few B. griseocollis, which in contrast have very short hair), or if the hair of T2 is extensively yellow, then it at least has many black hairs intermixed in the back corners at the sides (contrast B. impatiens, B. perplexus, B. vagans, B. sandersoni). Metasoma rather short and globular. Male 12–15 mm (0.46–0.59 inch). Eye similar in size and shape to the eye of any female bumble bee (contrast B. griseocollis, B. rufocinctus). Antenna of medium length, flagellum 3× longer than the scape. Hair color pattern similar to the queen/worker, but below the antenna a patch of yellow intermixed with black, metasomal T4–5 at the sides often with at least some yellow hair.

MICROSCOPIC CHARACTERS Queen metasomal T6 flat or with a weak lengthwise ridge just before the tip (contrast B. perplexus). Male genitalia with the penis valve sickle-shaped, at the far end back-curved as a long and narrow "sickle" at least 3× longer than broad, but distinctly flattened and more than 3× broader than thick, rounded and not expanded at the tip, the penis-valve angle on the underside of the shaft and to the side only slightly closer to the base than to the head of the penis valve, gonostylus with the inner (medial) edge concave.

OCCURRENCE

RANGE AND STATUS One of the most widespread and abundant species in the eastern US and adjacent southern Canada, throughout the Eastern Temperate Forest region, although less common on the southeastern US coastal plain, in the eastern Boreal Forest, and on the eastern Great Plains.

HABITAT Close to or within wooded areas, urban parks and gardens.

EXAMPLE FOOD PLANTSCampanula, Lonicera, Monarda, Prunus, Rhododendron, Rosa, Rubus, Tilia, Trifolium, Vaccinium, Vicia.

BEHAVIOR Nests mostly underground, though occasionally aboveground or in cavities. Males patrol circuits in search of mates. One of the species with colonies that end earliest in the summer.

PARASITISM BY OTHER BEES Host to B. citrinus, confirmed breeding record.

BOMBUS PERPLEXUS CRESSON, 1863

CONFUSING BUMBLE BEE

IDENTIFICATION

Eastern and northern, medium-tongued species. Most similar to B. impatiens, B. bimaculatus, B. vagans, and B. sandersoni (see also B. griseocollis, B. rufocinctus, and B. affinis). Evidence from DNA barcodes supports a close relationship between B. perplexus and taxa of the B. hypnorum-complex from northern Europe and Asia, although it appears to be a separate species.