While sightings should always be reported to Bumble Bee Watch, so they are accessible for conservation focused analysis, it’s not the same as being to tell like-minded folks about a cool sighting. New species for you? New County record? Track down one of those unsampled ecoregions to fill the vacuum of knowledge? See an unusual color morph? A challenging male?
Tell us about it!
This group contains some of my favorite species to encounter in the field. A couple of them can pose a bit of an ID challenge.
Two form bumble bee, B. bifarius
California bumble bee, B. californicus
Yellow-faced bumble bee, B. vosnesenskii
Obscure bumble bee, B. caliginosus
van Dyke bumble bee, B. vandykei
The Two form Bumble shows an inverted black triangle on her scutellum.
T1 = yellow/white
T2 = black
T3 = black
T4 = yellow/white
T5 = black
This form of the California bumble bee looks a lot like the next two species, except this species, the California bumble bee has a BLACK face.
The Yellow-faced bumble bee has a yellow face, scutum and T4. It’s stergites are black.
The Obscure bumble bee has a yellow face, scutum and T4. Stergites S4 and S5 have some white hairs.
On the van Dyke bumble, T3 shows yellow, in contrast to the Two form bumble bee, where T3 is black.
Stop the presses! As of July 29, 2020 Washington state has a new bumble bee species. Genetic analysis has determined that the population of the Two form bumble bee, Bombus bifarius in British Columbia has been recognized as a new, separate species. This new species is the Vancouver bumble bee, Bombus vancouverensis. This includes the population located in the San Juan Islands. Ergo, we have a new species!
What is not clear is what the actual differences are between the Vancouver bumble bee and the Two form bumble bee. At first I (DJ) thought that the individuals showing red on T2 and T3 were vancouverensis and the ones with T2 and T3 black were bifarius. Now it appears separating the two species in Washington may be a bit more challenging. It appears that the two color morphs are subspecies of the same species (B. vancouverensis)
As I am interpreting (please correct me if you know better!) the colorful color morph found in the San Juans Islands is the Vancouver bumble bee subspecies Bombus vancouverensis vancouverensis, while the form that we knew in the eastern part of Washington as the Two Form Bumble bee (Bombus bifarius) is now the Vancouver bumble bee subspecies Bombus vancouverensis nearcticus. For more discussion on this taxonomic question, please refer to the Two Form bumble bee page.
For a more complete discussion on field identification of the Bombus vancouverensis nearcticus subspecies refer to the Two Form bumble bee page.
Range, range, range. As far as I am currently aware, within Washington state, the Vancouver bumble bee Bombus vancouverensis vancouverensis subspecies is restricted to the area around the San Juan Islands. It has a similar color pattern to the Two Form bumble bee. It shows an inverted black triangle on the scutellum. T1 & T4 are yellow. T2 and T3 show a lot of red. T2 may show a black notch.
The red morph of the Yellow head bumble bee, which is also located in the San Juans, is somewhat similar, but it show red on T3 and T4. The Yellow head bumble bee also lacks an inverted black triangle.
The Black tail bumble bee shows red in the middle of the abdomen. T4 is black with a white line of hairs, no inverted black triangle.
The Frigid bumble bee, Bombus frigidus is a very rarely encountered bumble bee species in Washington. That may be because it is rarely looked for by individuals who go into the high country. That trend seems to be changing. I expect we will be adding additional locations to the map above. It has recently been detected at Harts Pass, by Rich Hatfield.
Key field marks are:
The Frigid bumble bee, Bombus frigidus is often found in association with two other high alpine specialists: the Forest bumble bee, Bombus sylvicola and the High country bumble bee, Bombus kirbiellus. All three show red on the abdomen.
The Frigid bumble bee, Bombus frigidus is easily distinguished from the Forest bumble bee because the red on a frigidus is at the end of the abdomen while the red on a sylvicola is on T2 and T3.
It is more of a challenge to visually separate the High country bumble bee from the Frigid bumble bee. They both have T1 and T2 yellow. The High country bumble bee, B. kirbiellus has black on the front half of T3, and yellow on the rear portion of T3. T4 and T5 are orange. Visually, this puts a break (yellow) between the black and red segments. This is in contrast with the Frigid bumble bee where black and red meet directly with no yellow line of separation.
Fuzzy-horned bumble bee, B. mixtus, and Sitka bumble bee, B. sitkensis are other similar species. A couple of key differences between kirbiellus and mixtus/sitkensis include:
As part of our quest to document all the bumble bee species found in Washington state the team of folks behind this website, David Jennings, Lisa Robinson and Don Rolfs established a state record for the High country bumble bee, Bombus kirbiellus.
In the summer of 2018 David organized an expedition to one of Washington’s high alpine regions, Horseshoe Pass. While in the high country Don netted and collected a bumble bee. We could not easily confirm it’s identity in the field, so it was collected. That bee was subsequently mounted and identified by Lisa. She keyed it out to be Bombus kirbiellus, better known as the High country bumble bee. Until we made this find, there had been no verifiable evidence of this species in Washington state.
Lisa reached out to Rich Hatfield, of the Xerces Society and he helped get our suspicions confirmed by having her identification collaborated by Dr. Paul H Williams at the Natural History Museum, London UK, a worldwide expert on the species.
Teamwork for the win!
Last year (2019), based on our finding, Rich Hatfield visited the site and wrote up his findings here: https://www.xerces.org/blog/bombus-kirbiellus . That would have been a fun trip to be on!
And in reading his article I learned something very useful! The preferred food plant of kirbiellus. Red paintbrush is an easy flower to spot on the landscape!
Again, teamwork for the win!
The High county bumble bee, Bombus kirbiellus, is as the name suggests a high elevation specialist. There are only a few places high enough with enough resources available for kirbiellus in Washington. The species is much more common in the high alpine country of Colorado up into Montana.
The scutum and scutellum are both yellow, with a black band between the wings. T1 and T2 are yellow, T3 is black with some white hairs in a line, T4 and T5 show orange or red.
The High country bumble bee may be found in association with two other high alpine specialists: Forest bumble bee, Bombus sylvicola and the Frigid bumble bee, Bombus frigidus. All three show red on the abdomen.
The High country bumble bee is easily distinguished from the Forest bumble bee because the red on a kirbiellus is at the end of the abdomen while the red on a sylvicola is on T2 and T3.
It is more of a challenge to visually separate the High country bumble bee from the Frigid bumble bee. They have T1 and T2 yellow. B. kirbiellus has black on the front half of T3, and some yellow on the rear portion of T3. T4 and T5 are orange. Visually, this puts a break (yellow) between the black and red segments. This is in contrast with the Frigid bumble bee where black and red meet directly with no yellow line of separation.
Fuzzy-horned bumble bee, B. mixtus, is another similar species. A couple of key differences between kirbiellus and mixtus include:
As can be seen below, the front of the thorax is yellow, not cloudy. T1 and T2 are yellow. There is a narrow yellow band breaking up the black/red interface on lower tergites.
What is a Cuckoo bumble bee?
To paraphrase Bumble Bees and Cuckoo Bumble Bees of California by Thorp, Horning, Jr and Dunning: Cuckoo bumble bees are social parasites without worker castes which usurp bumble bee nests and propagate themselves at the expense of their bumble bee hosts.
In other words, a queen cuckoo waits until another bumble bee species has an active nest with lots of workers. She invades the nest and kills the original queen. She then has the workers of the dead queen raise her eggs and larvae, rather than eggs and larvae of their own species. This has similarities to a cuckoo bird, which lays eggs in other birds’ nests.
Cuckoo bumble bees are the tanks of the bumble world: heavily armored and ready for conquest. Cuckoo queens lack a corbiculum (pollen basket) as they never gather pollen to take back to “their” nest.
Queens of non-cuckoo bumble bees collect pollen to feed their first set of workers each spring–so they need a corbiculum to collect and bring home pollen with which to raise the first set of workers. After the first set of workers hatch, the queen stays in the nest laying eggs while the workers go out foraging.
Cuckoos wait until other queens have established a nest with multiple generations of workers before they invade the colony, kill the existing queen and convince the workers to raise cuckoo bumble bee offspring.
Having said that, cuckoo bumbles are cool and part of the ecosystem.
They are a treat to encounter in the field.
Species are not bad or good.
Biodiversity is good.
Recognizing a cuckoo when we see it
If you see an unfamiliar bumble bee (cuckoos are rare relative to most other species in a given area) that seems very deliberate in its movements and walks from flower to flower, look closely at it’s rearmost legs. Is there a corbiculum present? Pollen basket?
If there isn’t then look closer. If no corbiculum, is it heavily armored? Behaviorally I (DJ) have noticed that, as a class, cuckoos often resist flying. They can fly, and do, but when they are on wildflowers they often walk from flower to flower rather than buzz from one to another as non-cuckoos do.
This may be due to the heavier weight of their thick exoskeleton. Because they are raised as warriors to go in and take over existing colonies, including killing the queen and any workers that rise to her defense, they are built much sturdier than non-cuckoos. It may take a lot more energy to fly around therefore more energy efficient to walk.
Cuckoo bumble species in Washington state include:
No pictures of Suckley bumble, B suckleyi available.
The Yellow bumble bee, Bombus fervidus is the primary species in this group. Tergites (upper abdomen) segments T1 thru T5 are yellow.
Another species to mention is van Dyle Bumble, B. vandykei. It traditionally falls in the “no red, yes stripes” group, but when I encounter it in the field I am often struck with how much yellow it shows.
Yellow head bumble females, B. flavifrons often show striking bright yellow on T1 and T2.
The yellow form of the California bumble bee, Bombus californicus also shows a lot of yellow.
The Nevada bumble bee has golden yellow on its thorax and T1, T2 and T3.
Other yellow bumbles that are commonly seen on the westside are drones/males of the Yellow head bumble bee B. flavifrons and the Fuzzy-horned bumble bee, B. mixtus.
Notice the rear (3rd) leg (above). Notice it is hairy and relatively round–no corbiculum. Big clue it is a male.
Males often have extra hairs on their upper lip (sound familiar?) giving them the appearance of have a mustache.
The thorax area in front of the wings (anterior thorax) is cloudy-a mixture of yellow and black hairs. The rear of the thorax (scutellum) is black. It may show some yellow on the sides as in the picture above.
The two front segments of the abdomen (T1, T2) are yellow. T3 is black. The end of the abdomen (rear of T4, T5, T6) has faint orange/pale hairs.
Two species that should be ruled out are Yellow head bumble bee, B. flavifrons and Fuzzy-horned bumble bee, B. mixtus. In the first instance, the pale hairs at the end of the tail can be missed (flavifrons). In the second, the red/pale hairs of sitkensis are not as prominent as exhibited by most B. mixtus. Mixtus may also show orange on T3.
As seen in the picture above, the anterior thorax is cloudy, T1 and T2 are yellow. T3 is black. T4 may show lots of black also, but will also have pale hairs. The pale hairs on T5 at the end of the abdomen are also visible.
The Forest bumble bee, Bombus sylvicola is a high altitude specialist. Here in Washington it is only found in the lofty elevations in the Olympics and Cascades. In a study done for the National Park Service, Bombus sylvicola, occurred only at sites between 1,113 and 2,023 meters in both parks.
The Forest bumble bee, Bombus sylvicola may be found in association with one or two other high alpine specialists: Frigid bumble bee, Bombus frigidus and the High country bumble bee, Bombus kirbiellus. All three show red on the abdomen. The Forest bumble bee appears to be the most common of the three species here in Washington state.
A general characteristic across these high altitude specialists relative to bumbles from lower elevations is long hair length. For this species, this would be relative to the Hunt bumble bee, Bombus huntii.
First, this is one species where range is a prime consideration. Unless you are pretty high in the mountains, don’t expect to encounter the Forest bumble bee. The Forest bumble bee has a yellow scutum and scutellum, and T2 & T3 are red.
The Forest bumble bee is easily distinguished from the Frigid bumble bee and the High Country bumble bee because the red on a frigidus and a kirbiellus is at the end of their abdomen while the red on a sylvicola is on T2 and T3. The same logic holds true for separating the Forest bumble bee from the Fuzzy-horned bumble bee, B. mixtus and the Sitka bumble bee, B. sitkensis.
The Forest bumble bee, B. sylvicola, has a color pattern similar to the Hunt bumble bee, B. huntii. They both have T1 yellow, T2 and T3 orange, T4 yellow. Luckily these two species can easily be separated based on range. The Forest bumble bee is a high alpine specialist while the Hunt bumble is comfortable in hot dry sites like the Dry Falls State Park lake basin.
The scutum is yellow in sylvicola. This can help distinguish between sylvicola and melanopygus, the Black tail bumble bee. The Black tail bumble has a cloudy scutum (black hairs mixed in with the yellow).
The Red-belted bumble bee, B. rufocinctus, has the potential to be confused with the Forest bumble bee. The Red-belted bumble bee shows T2 with some yellow. The Forest bumble bee has T2 all red.
To date, I (DJ) have not captured any images of sylvicola in Washington. The quest continues…
The Hunt bumble bee, Bombus huntii, is in my book one of the most spectacular bumbles we have in Washington. Their colors can be so brilliant. Once you encounter and identify this species, you will rarely have difficult identifying other such individuals.
At the photographic detail level, the field marks that distinguish the Hunt bumble bee, B. huntii are
Again, once you encounter one I doubt you will find them confusing to separate from other species. Sometimes the colors are faded on a older individual (check wing condition for an estimate of age) so the patterns of color need to be noted.
The main species in Washington with a similar color pattern is the Forest bumble bee, Bombus sylvicola. Key differences between the two species are first: range. The Forest bumble bee is a high altitude specialist while the Hunt bumble is a lowland dry country specialist. Think Dry Falls State Park. The second key difference is on T5. The T5 on a female Hunt bumble bee is all black. The T5 on a Forest bumble will show yellow, possibly with a black notch.
Based on where the majority of the detections are in the map above, the Hunt bumble bee is very much a dry country / east side species.
T1 = yellow, T2, T3 = orange, T4 = yellow, T5 black. The abdominal segments are relatively easy to count off in these pictures.
