Archive for the ‘Bumble Field ID’ Category

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.