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.
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 beeB. flavifrons and the Fuzzy-horned bumble bee, B. mixtus.
Yellow bumble bee, Bombus fervidus
Male flavifrons/mixtus, Note rearleg is hairy, no pollen, tibia more rounded
Nevada bumble bee, Bombus nevadensis
van Dyle Bumble, B. vandykei
Yellow head Bumble, B. flavifrons
male Yellow head bumble, B. flavifrons: could be (B. mixtus) NOT a Yellow bumble bee
Notice the rear (3rd) leg (above). Notice it is hairy and relatively round–no corbiculum. Big clue it is a male.
male Yellow head bumble, B. flavifrons: could be (B. mixtus) NOT a Yellow bumble bee (B. fervidus)
male Yellow head bumble, B. flavifrons: could be (B. mixtus)
Males often have extra hairs on their upper lip (sound familiar?) giving them the appearance of have a mustache.
Please reference the Embedded Range Maps page to better interpret # of observations per ecoregion.
The Morrison bumble bee, Bombus morrisoni is very rare in Washington state. There is evidence that the range of B morrisoni’s has been strongly contracting over the last decade or so. There is at least one population of morrisoni remaining in Washington and we hope we can locate others. Similar to what is being seen in Oregon, bumble bees in central Washington seem to be utilizing the urban areas. This may be climate change related, in that it has been so hot and dry many fewer nectar and pollen resources are available in the native landscapes so the urban centers with planted mints and other pollinator plants offer a greater diversity of flowering resources, throughout the full season.
If you encounter a suspected morrisoni in the field, please get good pictures. A positive ID can be made just from photographs for this species, so it would be better to use a non-lethal approach to documenting any individuals you encounter.
Field ID tips
This is a good sized bumble bee, similar to the Nevada bumble bee.
The Morrison bumble bee has a yellow scutum, alar and scutellum
T1 & T2 are yellow. T3 is mainly yellow but may show some black on the sides.
It has a short cheek.
Similar Species
The Nevada bumble bee is the most similar species. It will show a black dot between the wings and T3 will be all yellow. Relative to the Morrison bumble, nevadensis has a long cheek and therefor a very different face shape.
The yellow form of the California bumble bee will be very similar to the Yellow bumble bee, but shows some black on T2 and T3. There is disagreement about whether the California bumble bee is a subspecies of the Yellow. The two distinct forms come together in the Willamette Valley of Oregon, and you can see some of the mixed patterns that result.
The Nevada bumble bee, Bombus nevadensis, may well be our largest bumble bee in Washington state. Notice in the picture above its size relative to a native Iris. When I give talks I describe it as being “as large as my thumb”. That may be a bit of an exaggeration, but it is definitely a distinct presence when present.
Field ID tips
The Nevada bumble bee is identified by its larger size, the golden thorax with a black spot in the center, and T1 thru T3 a similar golden brown to the thorax. In some places, T1 may show some black (as in the photo below) but in general T1 is golden/yellow.
Nevada bumble bee, Bombus nevadensis
Similar Species
Similar species include Brown-belted bumble bee, Bombus griseocollis and the Morrison bumble bee, Bombus morrisoni.
The Brown belted bumble bee has brown on T2 or if yellow (queen) has black on the edges of the yellow on T2. T3 is black.
Morrison bumble bee lacks a black dot on the center of the abdomen. It also shows some yellow on T3. Relative to the long cheek of nevadensis, morrisoni has a short cheek.. If in doubt, look at the shape of the face. Hand lens can be handy. Once you have seen them both, you should feel confident in distinguishing between them.
Please reference the Embedded Range Maps page to better interpret # of observations per ecoregion.
Nevada bumble bee is an east side species. There are a few records on the west side, but it is not regularly seen there (that I am aware). I found it at the Turnbull NWR on a couple of separate occasions.
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.
Please reference the Embedded Range Maps page to better interpret # of observations per ecoregion.
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, 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.
van Dyke bumble bee, Bombus vandykei
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 plantsof the same species, resulting in successful pollination and increasing the “percent seed set” for the fertilized flower. Win-win for both plant and bee.
Please reference the Embedded Range Maps page to better interpret # of observations per ecoregion.
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.
van Dyke bumble bee, B. vandykei
Field ID Tips
A primary field mark to distinguish the van Dyke bumble from others is that the van Dyke shows T3 with yellow.
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.
van Dyke bumble bee, B. vandykei
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.
van Dyke bumble bee, B. vandykei
One might see the photo above and think Yellow head bumble bee, but this individual shows T2 as black.
