Posts Tagged ‘ID’

Half-black bumble bee, Bombus vagans

Friday, July 17th, 2020

The Half-black bumble bee, Bombus vagans, is an east side species in Washington state. While it is considered common across its range, it is a species that I do not encounter on a regular basis when bumbling around the east side of Washington state. When I do find one, it makes it a better field day for sure!

I have detected them in and around Davenport/Reardon, east of Spokane. Based on the limited number of detections shown on the map below, it has never been an easily found species in Washington state.

Having said that, I recently heard and saw video from Chris Loggers up in the Colville area of bushes swarming with B. vagans. Just goes to show: location, location, location!

In a talk by Dr Lincoln Best, he analyzed available Oregan Bumble Bee Atlas data and had few detections of B. vagans relative to many other species. If you see this species please report it to Bumble Bee Watch, iNaturalist or other citizen science documenting sites,

Please reference the Embedded Range Maps page to better interpret
# of observations per ecoregion.

This species is a good example of how much we are learning about bumble bees in Washington state. When the maps above were generated in 2016 they represented the best information easily available for bumbles in Washington state. Fast forward to 2020, where Chris Loggers, in the greater Colville area of the state sent us videos of bushes with well over 100 individual vagans foraging. A nice documented range extension!

Field ID tips

The Half-black bumble bee, Bombus vagans, is a small to medium sized eastside species in Washington. It is a smaller bee relative to the Nevada bumble bee and the Brown-belted bumble bee. The hind end of it’s abdomen is black, and T1 & T2 are yellow. The thorax is predominantly yellow also, usually with a black dot in the alar region. Look for a lump on its face where it might have a nose. I heard this tip from Lincoln Best during his recent (Jan 2021) talk on bumble bees in Oregon.

Similar Species

Similar species include Yellow head bumble bee, Bombus flavifrons and the Common eastern bumble bee, Bombus impatiens.

The Yellow head bumble bee has T1 and T2 yellow (sometimes with some black), but it’s thorax is much cloudier (black hairs mixed in with the yellow hairs). The Half-black bumble bee has the same color yellow on it’s thorax as it has on T1 and T2. The dark spot on the center of the thorax is also more pronounced on the Half-black bumble.

The Common eastern bumble bee is restricted to the west side of the state, so the two species do not overlap. The Common eastern bumble bee has a black T2. The T2 on the Half-black bumble bee is yellow..

White-shouldered bumble bee, Bombus appositus

Friday, July 17th, 2020

Field ID Tips

The White-shouldered bumble bee, Bombus appositus, is easily identified in the field by a combination of large size, bright white shoulder, black band between the wings and the entire abdomen a golden yellow.

Lisa’s father-in-law described this species as looking like they were wearing white shoulder pads. Sports analogies for the win!

It should be noted that there are three (3) additional color morphs of this species, at lease one of which can be encountered as close as Oregon’s Willamette Valley. They show mix of yellow or white on the scutum and yellow or white on the scutellum. Reference Bumble Bees of the Western United States for a visual.

Similar Species

No other species is similar in appearance.


The White-shouldered bumble bee, Bombus appositus, is one of our larger and more distinctive species. It is found mainly on the eastside, both on the east side of the Cascades, across north central Washington and then down and into the Blue Mountains, in the southeastern part of the state.

There have been detections over the years both on San Juan Island and also on the north side of the Olympic mountains, including as recently as July 2020, so it appears to not be solely restricted to the east side of the state.

van Dyke bumble bee, Bombus vandykei

Friday, July 17th, 2020
Van dyke bumble bee, Bombus vandykei, photo by Lisa Robinson

I (DJ) have many fond memories associated with this species. First and foremost, I got the photo (below) and learned this species on a multi-day trip into Stehekin, NCNP to do a NPS sponsored bio-blitz with some of the rockstars of the native bee world: Jamie Strange, H. Ikerd, Terry Griswold and Chris Looney, to name drop a few. What a nice introduction to some amazing people and fun evenings around the campfire getting to know each other.

Second, the encounter documented above also shows an important reason why native bees in general, and bumble bees in particular, are the best pollinators for the money–from the perspective of the plant. It demonstrates the foraging behavior of constancy.

The general way that constancy works is that a bumble bee leaves her nest colony for the first time as a worker and stumbles across a flower that offers the needed resources: pollen and nectar.

Not really knowing what she is doing, she figures out how to get her reward. Once she figures it out she looks for a similar flower (same plant species) and is able to figure out even faster how to extract the goods and move on. Now she is efficient with this flower type.

At that point she hones in on every flower of that plant species that still has resources to offer (if the flower has just been visited, the nectar is probably gone and will need to refill over some period of time) until she is fully loaded and goes back to the colony to unload, or runs out of untapped flowers of that species. At that point, if her load is not full, she will look for another flower type and repeat the process.

This behavior, going to the same flower type time again and again is called constancy. The reason why it is so important to the plant species involved is that this greatly increases the probability that the pollen will be spread to many other plants of the same species, resulting in successful pollination and increasing the “percent seed set” for the fertilized flower. Win-win for both plant and bee.

Field guides on bumble bees do a good job show the possible range of color combinations a given species may exhibit across its’ entire range. Trying to condense that into a visual that shows the full spectrum is challenging.

I say that because when I compare the individuals in these photos with the color schema’s shown in Bumble Bees of the Western United States, there are some inconsistencies.

These photos show that T1 sometimes shows yellow, not always black. The field guide shows the rear of the thorax (scutellum) to be black where these photos show some yellow present.

This is a good example of two different lessons. First, bee coloration is variable and may not align exactly with the examples in the book. Different than with most birds, for example.

Second, because color is variable, depending on the species, absolute identifications from photos may not be possible. Photographs rarely capture taxonomic level details like cheek shape. A collected specimen can be keyed out later as a voucher specimen of what was photographed. This should rarely be needed as a good working knowledge of our common species is relatively easy to acquire.

Field ID Tips

A primary field mark to distinguish the van Dyke bumble from others is that the van Dyke shows T3 with yellow.

Similar Species

Similar species to van Dyke bumble bee here in Washington include Two form bumble bee, Bombus bifarius and the yellow form of California bumble bee, Bombus californicus.

van Dyke bumble bee can be confused with Two form bumble bee mainly because they are fairly similar is size and both striped black and white/yellow. At least, I have been confused and assumed B. bifarius because bifarius is much more common. Part of the learning curve.

The van Dyke bumble has yellow on T3. T3 is black on the Two form bumble bee. The van Dyke bumble bee also lacks a black inverted triangle on the rear of its thorax.

Based on color patterns, van Dyke bumble bee and yellow forms of California bumble bee are similar. From my experience the van Dyke bumble bee is smaller bodied.

When you look at the pollen gathered on her corbiculum (photo above), you can see it is first one color (orange) and then it shifts to a 2nd color (washed out brown). The bumble started with collecting pollen (and nectar) from first one species, flower after flower (orange pollen). Finally, when it became too difficult to find flowers that had not already been visited, the individual bee switched to a 2nd species of flower and is now demonstrating constancy between flower types–as shown by the change in color of the pollen collected.

One might see the photo above and think Yellow head bumble bee, but this individual shows T2 as black.

Yellow-faced bumble bee, Bombus vosnesenskii

Friday, July 17th, 2020

The Yellow-faced bumble bee, Bombus vosnesenskii, is a common bumble bee on the west side of Washington state and appears to be spreading into the eastern portion. There is some speculation that the drastic decline in numbers of the Western bumble bee Bombus occidentalis, during the 1990s created an opportunity for expansion of the Yellow-faced bumble bee.

Please reference the Embedded Range Maps page to better interpret
# of observations per ecoregion.

Field ID tips

The Yellow-faced bumble bee is a species that can be easily recognized once one has encountered them in the field. They have colonies that may contain upwards of 1,000 individuals, in contrast to most bumble bee species which have totals more in the 300-500 range.

When you encounter B. vosnesenskii you rarely just find a single individual. More often they will be numerous in the area. With their bright black coat and the distinctive and strongly contrasting yellow on the head, front of thorax (scutum) and most eye catching, on T4, they can be identified with relative confidence. Their fur is relatively even, giving them a well groomed appearance.

Similar Species

Similar species include the California bumble bee, Bombus californicus and the Obscure bumble bee, Bombus caliginosus.

The California bumble bee lacks yellow on the face.

The Obscure bumble bee is a trickier identification challenge. The color patterns are similar, with yellow on face, front of thorax and T4. The fur on the Obscure bumble bee is less even and more shaggy. A definitive field mark is on the underside of the abdomen where the Obscure bumble bee shows white hairs.

An easier photo might be capturing the face to be able to discern if the individual has a long or short cheek/facial structure. Bombus caliginosis has a long cheek and therefor a longer face relative to Bombus vosnesenskii who has a much shorter cheek length and a shorter face.

Western bumble bee, Bombus occidentalis

Friday, July 17th, 2020

The Western bumble bee, Bombus occidentalis, was until recently the most widely distributed bumble bee species across Washington state. The range map below shows just how wide spread it was.

Then a disease outbreak spread from captive raised bumble bees used for tomato hothouse operations wiped out an estimated 95% or more of the wild population.

Even now, over two decades later, the numbers of Western bumble bees have not rebounded. They can reliably be found in and around Colville, but in other parts of the state encounters are much more sporadic.

Please reference the Embedded Range Maps page to better interpret
the # of observations per ecoregion.

Field ID Tips


The golden yellow scutum, black body and large white T4 and T5 are the classic field marks for the Western bumble bee. Also note the black head and face.
There is a color morph found in the Blue Mountains, and in Oregon, which has the scutellum (rear of the thorax) yellow, rather than black. It should still be distinctive as a Western bumble.

Similar Species

No other species has white on the end of its’ abdomen and golden yellow on the front of the thorax.

I do find that that in the field, Western bumble bees can feel a bit like Bald faced hornets, with white at the end of the abdomen. Could it be an example of mullerian mimicry?

California bumble bee, Bombus californicus

Friday, July 17th, 2020

The California bumble bee, Bombus californicus, has two distinct color morphs. The first is similar to the Yellow-Faced bumble bee, Bombus vosnesenskii, but California bumble bee lacks yellow hairs on the face.

The California bumble bee, Bombus californicus can be found on both sides of the Washington Cascades. On the west side, it is a regular member of the pollinating community associated with our native prairies, as documented by Dr. Susan Waters and her team conducting pollinator pathway studies on the remnants of our west side prairie habitats.

californicus or fervidus?

Bumble bee taxonomists are having discussions about whether Bombus californicus is a full species or a subspecies of Bombus fervidus, based on gene pheneology and mitochondrial markers.  Bombus californicus shares the same mitochondrial marker cytochrome-oxidase I (COI) with B. fervidus, supporting the single species perspective (Williams, et al. 2014).

Those findings are not aligned with results from a five (5) gene phylogeny study which concluded that B. californicus and B. fervidus were different species (Cameron et al, 2007).

The two species/forms meet along the eastern side of Columbia gorge.  I have not sampled there myself yet, but my understanding is that the individuals seen fit the field marks for one or the other species, suggesting some level of cross-breeding barrier.

Reasons to list B. californicus as a separate species on this site comes from two totally unrelated personal experiences (DJ).  First, when I was an young birder I learned the Oregon Junco as part of my wildlife biology training.  At that time there were two distinctly different forms: slate-side and Oregon (now there are at least 4!).  Because I only had to learn “Oregon Junco”, my brain has refused to easily remember the distinguishing characteristics—sad but true. We learn to the test. Sadly.

The second reason is political.  Our state and federal wildlife conservation laws offer much more protection for distinct species rather than subspecies or ecotypes.  By recognizing these as distinct species, it may make it easier to get one of them the protection they deserve when needed.

Third, what is a species? I once thought there were firm barriers between species, but then I took a Dendrology class in Forestry School and had learn the southern Oaks…and also learned how oaks hybridized across “species” to the extent that our responses to questions required identifying which two species were likely involved in the hybrid individual in question. Some very nice work was done on finches in the Galapagos Islands (Beak of the Finch). I find myself to be a splitter, focusing on adaptations to local conditions driving natural selection.

Field ID tips

The California bumble bee, Bombus californicus, has two distinct color morphs.
The black form has a yellow scutum and yellow T4. The face is black (this is a key field mark).
The yellow form is predominantly yellow and shows some black on T2 and T3. It also has a black alar (wing band)

Similar Species

Similar species for the black form are Yellow-faced bumble bee, Bombus vosnesenskii and the Obscure bumble bee, Bombus caliginosis. The California bumble bee is easily separated from these two similar species because it is the only one of the three with a black face.

The yellow form is very similar to the Yellow bumble bee, Bombus fervidus. The Yellow bumble bee has a totally yellow abdomen (T1 thru T4 yellow). The dark bands on abdominal tergites T2 and T3 of the California bumble bee are the key to separating the yellow form of this species from the Yellow bumble, B. fervidus.

This species and the Yellow bumble bee are sharing landscape level habitats in the Willamette Valley of Oregon. Seems like a great site for a field trip!

Two form bumble bee, Bombus bifarius

Friday, July 17th, 2020

aka Vancouver bumble bee, Bombus vancouverensis nearcticus

The Two form bumble bee is (was) a small bodied species common on the east side of Washington state. It can be found on the west side as well, but seems to thrive on the east side. Note the black triangle pointed at the abdomen, on the rear of the thorax (scutellum).

There is some confusion after the Vancouver bumble bee, Bombus vancouverensis, was separated from Bombus bifarius as to how to separate them and where do the two species occur separately and where do they overlap. While I (DJ) first thought B. vancouverensis was the red form found in the San Juans Islands and up north in the central part of British Columbia, now it seems that it may not be a correlation between external colors and species distinction.

I had the pleasure of putting this question to Dr. James Strange and his response was: “As for bifarius in eastern WA, they should all be considered B. vancouverensis (for now).  A few of us started to look at splitting vancouverensis into two species: vancouverensis and nearcticus but we don’t have the data to do that yet.  We will have to see if the data bears out the split, but for the foreseeable future vancouverensis is the name that has taxonomic precedence”.

Please reference the Vancouver bumble bee page for more discussion on the new taxonomy.




Field ID tips

Identification of the Two form bumble bee, Bombus bifarius is fairly straight forward for the most common color morph in Washington. There is a black band between the wings and a black inverted triangle coming from that black band down to the abodomen.

The abdomen is distinctly striped:

  • T1 = yellow or white
  • T2 = black (maybe some red)
  • T3 = black (maybe some red)
  • T4 = yellow or white
  • T5 = black

Similar Species

The Red-belted bumble bee, B. rufocinctus, with its’ many color morphs can be confusing to separate. Red-belted lacks a black inverted triangle, and T2 should show some yellow. Bombus rufocinctus has a very short cheek and therefor a very short face.

The non-standard color morphs of B. bifarius all show the black inverted triangle below the black wing band. The abdomen however may have some or lots of red on T2 and/or T3.

Yellow head bumble bee, Bombus flavifrons

Friday, July 17th, 2020

The Yellow head bumble bee, Bombus flavifrons, is a common bumble bee in Thurston county. It is found around the state, but is most commonly encountered on the west side of Washington.

Field ID Tips

The thorax is cloudy.

T1 and T2 are often bright yellow, contrasting with the black rear.

The majority of individuals I have encountered have black on T3, T4 and T5.
In the San Juan Islands, and I hear from a reliable source, around the Mountain Loop highway, T3 may be replaced with red. An example is shown at the bottom of this page.

Similar Species

Similar species include the Central bumble bee, Bombus centralis and the Sitka bumble bee, Bombus sitkensis.

The Central bumble bee has the scutum (front of the thorax) yellow, not cloudy. T3 and T4 will be red, with T5 black.

The Sitka bumble bee will have pale reddish hairs on T 4 and T5. These can be a bit subtle.

Male Yellow head bumble bees

are bright yellow and relatively common in the summer time. They are similar to males of Bombus mixtus.

Look for hairy legs with no pollen attached.

Red-belted bumble bee, Bombus rufocinctus

Friday, July 17th, 2020

The Red-belted bumble, Bombus rufocinctus, is the species of bumble in Washington state that show the greatest diversity of color patterns. If you check Bumble Bees of the Western United States, by Koch et al, you will see that not all red-belted bumbles even show red! This is one of my most challenging species to identify. Catching one to look at under a hand lens, to confirm cheek shape may be helpful.

To quote from that reference guide: “similar to many color patterns shown by both western and eastern NA bumble bees…small bodied, short-haired, short face.” emphasis added.

Field ID Tips

I think that maybe identifying Red-belted bumble bees may be easier than I have made it out to be. They have been the species “most mysterious” from a confident field ID perspective–since there is so much variability in their color patterns.

Having said that, T2 usually shows some level of yellow, and at least as I know so far, the color morphs in Washington are all of the “shows some red” group, rather than the forms where the red is black. So, T2 with yellow, some red on abdomen.

What else. Small bodied bee, hair length relatively short and even. Very short cheek–this is one time where being able to capture an individual, cool it briefly and example the cheek ratio can be very helpful for a confidential identification.

Similar species

The next element is process of elimination from other possible bumble bees. Within Washington, there are four possible bumble species that might cause confusion: the Black tail bumble bee, the Two form bumble bee, the Hunt bumble bee and the Forest bumble bee.

The Red-belted can be distinguished from the Black tail bumble bee, B. melanopygus because the Red-belted’s scutum is yellow, while the Black tail scutum is cloudy.

The Red-belted can be separated from the Two form bumble bee, B. bifarious, because the Red-belted lacks the black inverted triangle.

The Red-belted can be separated from the Hunt bumble bee, B. huntii and the Forest bumble bee, B. sylvicola because those two species have T2=Red

The Red-belted bumble is primarily found in eastern parts of Washington. The Blue mountains are a good place to look for them.

Fogbelt / Obscure bumble bee, Bombus caliginosis

Monday, July 13th, 2020

The Fogbelt bumble bee, Bombus caliginosus, is a species I have found mainly on the southern slopes of the Olympic Mountains. It is not uncommon in that area, but is easily confused with a similar looking species, the Yellow-faced bumble bee, Bombus vosnesenskii.

The common name gives you a sense of it’s preferred habitat.

Please reference the Embedded Range Maps page to better interpret
# of observations per ecoregion.

Field ID tips

The Fogbelt bumble bee has a yellow face with a long cheek, yellow scutum and yellow on T4, with the rest of the bee being black. A key field mark can only be seen with a view of the underside of the abdomen. As seen in the pictures above and below, B. caliginosus shows white hairs on its stergites (underside of abdomen).

Similar Species

The only similar species to the Fogbelt / Obscure bumble bee is the Yellow-faced bumble bee, B. vosnesenskii. They both show yellow face, yellow scutum and yellow T4. A primary way to distinguish between the two is to look on the underside of the abodomen (stergites). Vosnesenskii has a solid black underside. As seen in the picture below, caliginosus show white hairs on its stergites (underside of abdomen). A more subtle field mark is that B. vosnesenskii has relatively even hairs while the Obscure bumble bee has hair a little more unkempt.