The Amateur Anthecologist: Bumble Bees of Vesper Meadow

Bombus vandykei on a native Phacelia

Bumble bees are some of the most conspicuous of the bees. Fast flying, buzzing balls of fuzz hurtle from flower to flower and can bee seen, or heard, from a distance. This may be part of why they are many folks favorite bees. While I could never choose a favorite bee, bumble bees are charismatic and fascinating. While the United States boasts around 40 species of Bombus (the genus to which bumble bees belong), there are roughly 30 species native to just the Pacific Northwest (Idaho, Oregon, and Washington). At least 15 species call Southern Oregon home, and many of these have been identified from the Vesper Meadow Restoration Preserve in Ashland.

Prime bumble bee habitat: Wyethia angustifolia blooming in part of the Vesper Meadow Restoration Preserve

Vesper Meadow Restoration Preserve

Vesper Meadow is a privately owned 403 acre upland wet meadow in the heart of the Cascade-Siskiyou National Monument. The Vesper Meadow Education Program, which operates at the meadow and surrounding forest acreage, brings together scientists, students of all ages, and the public to study the local ecosystem and cultural significance of the land. One of the goals of the Preserve is to monitor wildlife of all sorts, from birds to plants to insects. Pollinators, especially butterflies and bees, are also being documented and monitored by organizing focused bioblitzes. Typically taking place over the course of a single day, a bioblitz is when a group of volunteer citizen scientists attempt to record as many living species as possible in a given area.

Bombus vosnesenskii on Solidago at Vesper Meadow
2021 Bumble Blitz at Vesper Meadow

Vesper Meadow is hosting a targeted bumble bee survey on Sunday, June 27th (from 10:00am to 2:00pm). This will be the second annual Bumble Blitz. Attendees will learn the basics of bumble bee identification, how to net a bumble bee, become acquainted with some of our native flora, and contribute to science! Also, it's beautiful there. Get some fresh air, meet fellow bee nerds, and enjoy the wilderness. If you plan on attending, please RSVP on the Vesper Meadow website.

Bombus flavifrons on Agastache urticifolia

Bumble Bees 101

I will now provide a basic introduction to some of the bumble bees we've identified from Vesper Meadow. But first, a little about bumble bees. Bumble bees (genus Bombus) are cousins of the honeybees (genus Apis). Bumble bees are found around the world in temperate regions, most north of the equator (with the exception of South America where a handful of species are found), with the highest species richness from the Tibetan Plateau westward to the Alps. Most species are eusocial, like honeybees, except a smaller proportion of species which are social parasites (subgenus Psithyrus, they expropriate established nests of non-parasitic species for their own reproductive gains). In contrast, honeybees aren't native to the Americas and the genus Apis contains no social parasites.

Bombus californicus on Wyethia angustifolia
Bumble Bee Life Cycle

Bumble bee colonies have an annual lifecycle. At the start of the season (anywhere between spring and summer, exactly when depends on the species) a queen emerges from her hibernaculum and seeks both nourishment from flowers and an abandoned rodent burrow or grass tussock to initiate a nest in. Once she finds a suitable nest location, she rears a batch of miniature workers which take over some of the foraging duties of the queen, allowing her to remain in the nest more and more. Eventually the colony has many workers (between 50 and 500, though usually less than 100) and the queen remains in the nest for the rest of her life. Towards the end of the lifecycle of the colony, new queens and drones (males) are produced, which leave the nest to find mates from other colonies. Following mating, the drones die and the newly mated queens seek a place to shelter over winter. The original colony and queen dies, and only the new queens last the following year to renew the cycle.

Bombus bifarius s.l. (B. vancouverensis nearcticus)
Vesper Meadow Bumble Bees

I've caught at least seven species of Bombus at Vesper Meadow, in addition to perhaps three or four additional species which have yet to be identified. Bombus californicus (syn. fervidus), flavifrons, melanopygus (syn. edwardsii), mixtus, nevadensis, vancouverensis nearcticus (syn. bifarius s.l.), and vosnesenskii have all been identified, yet caliginosus and vandykei (very close mimics of vosnesenskii) may possibly be found at or around Vesper Meadow. The white-shouldered bumble bee, B. appositus, is also found in the area (likely at Vesper Meadow) but it is uncommon. Additionally, there has been a single sighting of the Western bumble bee, B. occidentalis, but no sightings since to my knowledge.

Bombus flavifrons

There also may be one or two of the socially parasitic bumble bees, subgenus Psithyrus, though no sightings or specimens have been confirmed as of this writing. The Oregon Bee Atlas expects to find the Fernald cuckoo bumble bee (B. fernaldae, syn. flavidus) and the Indiscriminate cuckoo bumble bee (B. insularis) in Oregon, but very few specimens have been vouchered. Social parasitic bumble bees have only two castes, female ("queens") and male, unlike other bumble bees which have queens, workers, and males. Rather than building their own nests, Psithyrus females (not technically queens since there is no worker caste) invade established nests and take them over, using the host workers to rear her young. This results in killing the colony since workers are no longer produced, only reproductive males and females of the social parasites. This seems harsh, but their presence would indicate a healthy host population. Psithyrus females can be identified by having no corbiculae.

Species Accounts

The following are a selection of bees I've photographed or collected for the Oregon Bee Atlas and Vesper Meadow Bumble Blitz. For the Bumble Blitz, we will be using the capture, chill, release method. This involves netting bees, putting them in vials, and chilling them in a cooler so we can take detailed photos of them for identification. This is in contrast to netting bees, placing them in a kill jar (it's more humane than it sounds), and pinning them for identification under a microscope. Both collection methods have pros and cons. There are some bees that are very difficult to identify in the field, which is where pinned specimens may be superior. However, catch-and-release doesn't come with any moral ambiguity. As you will notice, photos don't always capture every characteristic necessary to assuredly identify some species. The best advice is to take as many good photos as possible, and hope you've captured the right angles.

White-Shouldered Bumble Bee - Bombus appositus

Bombus appositus

The white-shouldered bumble bee, Bombus appositus, has a general appearance of being well groomed with short, even hair all over. As the common name suggests, this bee has white patches on the anterior of the thorax, with a black band between the wing bases. The face and posterior of the thorax is either white or yellow, with the abdomen completely yellow or tawny buff. The white-shouldered bumble bee nests both underground and on the surface, such as within dense grass tussocks.

California Bumble Bee - Bombus californicus

Bombus californicus

Bombus californicus (syn. B. fervidus californicus) is very similar to both vosnesenskii and vandykei, all are black with yellow bands on the thorax and a yellow band of hair towards the tip of the abdomen on the third or fourth segments (also called tergites). B. californicus differs from the lookalikes by having a completely black head and a cheek longer than broad. They nest on the surface or aboveground, occasionally underground. Nests may be found in haystacks, abandoned mouse nests, or birdhouses. They are said to be one of the more aggressive species, most likely when nests are disturbed.

Yellow-Fronted Bumble Bee - Bombus flavifrons

Bombus flavifrons female

Bombus flavifrons females are usually characterized by yellow and black hairs intermixed on the face, and intermixed yellow and black on the anterior of the thorax. The first two tergite have yellow bands while the third and forth tergite have either orange or black. The forms I've seen at Vesper Meadow usually have black bands with few orange hairs intermixed, appearing dull orange. Similar to californicus, they have a relatively long cheek (malar space longer than wide).

Bombus flavifrons male

In contrast to females, male flavifrons are almost entirely yellow or sometimes have black or orange hairs intermixed in the last few tergites. This species nests primarily underground, utilizing abandoned rodent burrows.

Fuzzy-Horned Bumble Bee - Bombus mixtus

Bombus mixtus

Bombus mixtus has yellow and black hairs intermixed on the face and thorax. The first abdominal tergite is always yellow, followed by a black band and the fourth/fifth tergites orange, sometimes appearing dull and intermixed with yellow hairs. B. mixtus is sometimes known as the fuzzy-horned bumble bee because the males have tufts of hair jutting from their flagellum (segments of the antennae), though they're only visible at certain angles under magnification. They are flexible in their nesting locations, nesting above- and belowground.

Black-Tailed Bumble Bee - Bombus melanopygus (syn. edwardsii)

Bombus melanopygus (syn. edwardsii)

As seems to be the case with many of the Western bumble bees, Bombus melanopygus has two distinct color morphs. The morph pictured here has no orange, and is sometimes considered a separate species, B. edwardsii, depending on the authority. The black-tailed bumble bee, B. melanopygus, is so named since the last tergite is always black. The hairs on the head are usually yellow or yellow intermixed with black. Similarly, the anterior of the thorax is mostly yellow with black intermixed, followed by a black band, with yellow hairs on the thorax posterior. Note that the corbicular fringes are mostly black (compared to vancouverensis nearcticus which has orange corbicular fringes) The abdomen always has yellow on the first tergite, usually followed by orange on the second and third tergites.

Bombus melanopygus (syn. edwardsii)

The Bombus edwardsii color form of melanopygus replaces orange with black on tergites two and three. The fourth and fifth tergites have yellow creeping inwards from the sides. B. vancouverensis nearcticus is very similar to the edwardsii color form, but nearcticus (almost) always has black on the last two tergites in females. The black-tailed bumble bee nests wherever, in birdhouses, housing insulation, abandoned rodent burrows, or wherever they deem fit.

Nevada Bumble Bee - Bombus nevadensis

Bombus nevadensis queen

Bombus nevadensis is similar to B. griseocollis which is more common at lower elevations. B. nevadensis has a look of being clean cut. It seems more brown than yellow compared to other bumble bees in the area. Hair on the face is usually black, sometimes with a few yellow hairs intermixed. There is usually a black spot or band between the wings with many intermixed yellow and black hairs around it. The sides of the thorax are black. The second and third tergites always yellow, while the first tergite is either black or yellow. The last few segments are always black, except for males which have orange at the tip. These large bees are most often ground nesters.

Two-Formed Bumble Bee - Bombus bifarius s.l. (syn. vancouverensis nearcticus)

Bombus vancouverensis nearcticus (syn. B. bifarius s.l.)

Bombus vancouverensis nearcticus (sometimes shortened to B. nearcticus) and v. vancouverensis were recently split from bifarius, the two-form bumble bee (see Ghisbain et al 2020). According to genetic analysis, bifarius s.s. is restricted to the Colorado Plateau and surrounding regions east of the Rockies, while vancouverensis nearcticus is found from the San Juaquin Valley in California and as far north as British Colombia. The third species, v. vancouverensis is restricted to Northwestern Washington and Southwestern B.C. If you don't follow, don't worry. Oregon only has v. nearcticus, which has no orange on the abdomen, while both bifarius s.s. and v. vancouverensis both have red.

Bombus vancouverensis nearcticus

Bombus vancouverensis nearcticus has a characteristic black notch in the center of the yellow band on the posterior of the thorax. There is a yellow band on the fourth tergite while the fifth and sixth tergites are always black. Compare with edwardsii (syn. melanopygus) which has yellow on the sides of the fifth tergite. This species will also have orange fringes on the corbicula while edwardsii will usually have black hairs, sometimes tipped with orange. The two-form bumble bee is primarily an underground nester, though they occasionally nest on the surface.

Yellow-Faced Bumble Bee - Bombus vosnesenskii

(including descriptions for vandykei and caliginosus)

Bombus vosnesenskii

Bombus vosnesenskii, vandykei, and caliginosus are all incredibly similar. All three have yellow faces and yellow shoulders, with a yellow band on the abdomen. With vosnesenskii and caliginosus, the yellow abdominal band will be on the fourth tergite while vandykei will have the yellow band on the third tergite. Where in vosnesenskii the sternum (underside of the abdomen) will be entirely black, caliginosus will have pale yellow fringes on the fourth sternite. I've also noticed that vandykei males are often completely yellow and probably indistinguishable from male flavifrons. Both vosnesenskii and vandykei nest underground, while caliginosus will nest underground or in abandoned bird nests.

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Thanks for taking the time to read this. This is no substitute for a proper identification guide, but rather an attempt at an introduction. I hope you can make it to the 2021 Bumble Blitz, so if you can please RSVP!