The Western Bumble Bee was once very common in the western United States and western Canada. The workers have three main color variations. These bees can still be found in the northern and eastern parts of their historic range, but the once common populations from southern British Columbia to central California have nearly disappeared. This bumble bee is an excellent pollinator of greenhouse tomatoes and cranberries, and has been commercially reared to pollinate these crops. In the past, it has also been an important pollinator of alfalfa, avocado, apples, cherries, blackberries, and blueberry.

IDENTIFICATION

In order to properly identify bumble bees, you need to first determine whether the bee you are examining is male or female. There are three different types of bumble bees you will encounter: workers, queens, and males. Both queens and workers are female. In most cases, queens and workers have similar coloration and physical features, except that queens are much larger. Males can differ in coloration from females of the same species, as well as other physical characteristics. Once you have determined the sex of your bee, you will want to identify whether it is a Western Bumble Bee or another species of bee.

Bombus occidentalis has many different color variations. On this page, we discuss the characteristics and distribution of the three most common color variants. There are many intermediate combinations of these three color forms that may also be encountered. The first color variant is found from northern California, north to British Columbia and east to southwest Saskatchewan and to Montana. This color variant has yellow hair on the front part of its thorax. The first through the basal section of the fourth abdominal segments have black hair. The lower edge of the fourth abdominal segment and segment 5 are whitish. The sixth segment often has sparse, whitish hairs, but may still appear black because the bee's black exoskeleton shows through the hairs. In some cases, the sixth segment may instead appear to be whitish. Their hair is entirely black on the head. A second color variant of B. occidentalis is found along the central coast in California. It differs from the first in having yellow hair on the sides of the second abdominal segment and all of the third and reddish brown hair on segment five. A third variety of B. occidentalis is found from the Rocky Mountains to Alaska. It differs from the first in having yellow hair on the thorax behind the wings and yellow on the rear of the second and all of the third abdominal segments. Coloration of males is similar except that males have pale yellowish hair on the front of the face and the top of the head has pale yellowish hairs in the middle, with a few black hairs on the sides.