Thursday, June 7, 2012

The Bumble Bees of Thurston County

Bombus mixtus and Bombus melanopygus workers on allium
Bumble bees are the most readily recognizable of all native pollinating insects. They're like pandas; terrific ambassadors to the natural world. And even though they have the ability to sting, they are surprisingly tolerant of humans when away from their nests. Yet the average person knows very little about them, and even bumble bee experts (few and far between) have only recently begun to get a handle on the complexities of their taxonomy, ranges and habitat.

This is true on the local level as well. We know for sure there are at least eight species of bumble bees indigenous to Thurston County and probably more. In an effort to educate the public about these amazing insects, we would like to share with you our introductory identification guide to the Bumble Bees of Thurston County.
Probable male Bombus flavifrons
Photographing and identifying bumble bees in the field can be surprisingly challenging. Some bumble bee species look very similar, if not identical to each other. Bumble bees of different species occasionally interbreed. Bumble bees move very quickly. They typically forage on blossoms for only the briefest moment in time before moving on to the next flower. The flowers they forage on are often close to the ground. The female and male bumble bees of some species look quite different. Finally, bumble bees of the same species and sex can be of dramatically different sizes!
Bombus mixtus queen on rhody
The queens are the largest bumble bees of each species to be seen all year. The first generation of worker bees that the queen raises herself can be really tiny - no larger than a pea. As the season advances and the number of workers in the nest grows and more food resources become available, subsequent generations get larger. In the spring, this can lead to the the rather puzzling sight of seeing two same-species bumble bees on the same plant, one about the size of a large marble (a queen), and one pea-sized (first generation).

We have endeavored to take the best bumble bee photos possible for this guide, but for all the reasons above, it's an ongoing process. As more and better shots become availble, we'll post them.  For identification purposes, the three main bumble bee body parts are: The head; the middle section called the thorax (where the wings attach); and the largest hind segment which is the abdomen.  Worker bees are always female and resemble the queen.

The Bumble Bees of Thurston County:

Bombus vosnesenski, or Yellow-faced Bumblebee. Very common from early February until mid-November, B. vosnesenskii is one of our largest queens. A big black body, with yellow face, a yellow bar across the upper thorax and a thin yellow stripe near the end of the abdomen. From February to late June, you can see a distinctive behavior: these large queens slowly patrol the grass and gardens in a loud, droning, low altitude flight looking for abandoned mouse holes in which to make their nests.                                                
Bombus vosnesenskii queen on rhody
Bombus californicus or Black-faced Bumblebee. A late-emerging queen, this species is first seen in late June and vanishes by October. They are uncommon here. The queen is very large, even slightly bigger than the Yellow-faced bumble bee queen. B. californicus has a large, shiny black prow of a face, with a thick pale yellow stripe across the thorax and a thin yellow stripe near the end of the abdomen. Preferred nectar plants we have observed this bee on are germander, lamb’s ears and caryopteris, although the one in the photo happens to be on monarda (bee balm), another favorite.
  Bombus californicus on Monarda, ("Bee Balm")
Bombus melanopygus or Black-rumped Bumble bee. We think this species should be called the "Red-belted Bumble bee" for the bright red band around its middle. B. melanopygus is our earliest emerging queen; the earliest date we have seen her is January 21st (during an unusual warm spell one winter). These bees love rhododendrons and in May can be seen using all kinds of rhodies, faces buried deep in the flowers' nectaries and frenetically gathering pollen. By early June, the rhododendrons are done, and so, too, are the melanopygus bumble bees; it is rare to see one past June.

Bombus melanopygus worker on rhody
Bombus melanopygus is distinctive: a yellow head, a mostly black thorax, with some yellow further back, then a wide, brick-red cumberbund across the upper abdomen, followed by black. The aposomatic (warning) coloration of this bee befits its feisty nature. If you get too close to a B. melanopygus nest, watch out!

In early spring the queen of this species loves crocuses, heather and pussywillows. On a 50+ degree day in February, with full sun, from 2- 4 pm, she can usually be found seeking nectar and pollen at these flowers. 
Bombus melanopygus queen on crocus
Bombus occidentalis is officially known as the Western Bumble Bee, though we think of it as the "white butt" bee. It's a large bee that used to be common in Thurston County, but in the last 10 years it has disappeared from much of its previous habitat and is considered to be in trouble. We have been observing local bumble bees since 2008, and have never seen one.                    
Bombus occidentalis      (Xerces Society photo)

For this reason the Xerces Society is tracking any sightings. Look for a large black bee with a black face, a yellow stripe across the thorax and upper abdomen, followed by a thick white patch that covers the tail. The white patch is distinctive and unmistakable.
If you see this bee, try to take a picture. Call us at 352-9009 and contact the Xerces Society at                      

Bombus mixtus is a smallish bee, even the queen is pretty small . The first queens emerge in late March and the workers can be seen throughout the summer.

On first glance B. mixtus is mostly a small, fuzzy yellow bee. But on closer inspection, on the abdomen you will notice a thick yellow stripe, followed by a mostly black thick stripe, and finally, at the business end (stinger-tail), pale-orange pile.
Bombus mixtus male on lavender
These bees have short tongues, which mean you are less likely to find them nectaring at deep flowers. They are famous for "nectar-robbing", which means they chew holes in flowers with hard to reach nectar, sticking their tongues in to feed and bypassing the pollen. The flower thus gets cheated of pollination services.
Bombus mixtus female nectar-robbing columbine blossom
Bombus nevadensis nevadensis is the Nevada Bumblebee. We’ve only see it once: a spectacular HUGE queen had just emerged in late July and we found her nectaring on lavender. We let her go (after taking a few photos) and we’ve not seen her or her progeny since. In four years of serious BB watching, this is our only sighting, so at least in Thurston County it is a very rare bee. 
Bombus nevadensis queen on lavender

These are our biggest bumblebees. A glossy black face, a thorax covered very densely with mustard-yellow pile except for a central black spot, and an abdomen that is also covered with thick yellow pile, except for black pile at the business end.
Bombus nevadensis queen
Bombus sitkensis or Sitka bumblebee. We are still learning about this bee. The queen probably emerges in mid April. She is medium sized; her face is black with a few yellow tufts, her thorax has a circlet of pale yellow hair and a very large black central spot. One thing we’ve noticed is that she has quite a bit of yellow hair at the base of her wings, which sort of looks like armpit hair.

The first part of her abdomen has a lemony yellow pile, followed by mostly black. The very end of her abdomen has some scattered, distinctly dark red rusty hairs. This is a key field mark,and is also hard to see without getting within striking distance of her stinger.
Bombus sitkensis worker

Bombus sitkensis worker

Bombus flavifrons - This bee looks very much like Bombus sitkensis, and quite frankly, we're still trying to sort out the differences.  The one diagnostic is the lack of rusty-colored hairs on the very end of the abdomen.

Probable Bombus flavifrons
Probable Bombus flavifrons

Other bumble bees of Thurston County:

Bombus rufocinctus - We haven't seen this bee yet, but we know its here. When we have photos we'll post them.

Bombus bifarius - Another bee we know is here, but haven't seen yet.

For those interested in learning more about our native bumble bees, two excellent identification guides have recently been become available:

Bumblebees of Washington


Bumble Bees of the Western United States

Several of the bees here we have written on in more depth in earlier posts.  They can be found here:
We hope you enjoy and use this guide.  Please feel free to contact us with feedback and questions about bumble bees. We'd like to continue to expand our knowledge of these fascinating and important pollinators. 

Text written by Janet and Nancy Partlow
Except for Bombus occidentalis, all photos taken by Nancy Partlow


  1. Thank you so much for this guide and the links! I discovered your blog last week after my three year old and I began watching the bees on the flowers in our backyard and came across a queen yellow-faced bumblebee. I'm looking forward to a summer of identifying the bees in our backyard.

  2. I am so happy and grateful for this blog! I have fallen in love with my local bumblebees over the past five years and have noticed patterns of when different species emerge. I am hooked and want to learn more. I'd love to learn how to identify bees on the wing. I would love a workshop!

  3. What a great article on local bees! I just watched Jerry the Bee Man scoop up some bees from neighbor's attic & fun to find out which type of bee it was (Bombus melanopygus). I had 3 types of bees buzzing around me while working on my raspberry canes, the other day. We all did our respective jobs and I enjoyed the buzz.

  4. I love your blog. Wish you had some recent things. I have been seeing Bombus huntii and notice you don't have it listed as a Thurston County bee yet.

    It was visiting a Cotoneaster species in Panorama.
    Sally Vogel

  5. SallyV, we are glad you love our blog. Bombus huntii is not found west of the Cascades, but closely resembles B. melanopygus, which is quite common at this time of year in Puget Sound country.