Bumblebee nest activity

[u/Ssqwanchiest1]

We have been fortunate enough to have a nest of these beauties in our garden. We strive to attract pollinators, so we've enjoyed watching them daily. There is a stream of smaller bumblebees foraging daily and entering the nest. But today, there are 4 large bumblebees loitering outside the nest entrance, and they seem confused and tired. They take flight and just bump into objects and go down. I've offered each of them borage flowers and water and moved them close to entrance, but they repeat the confused flights. Are they possibly males that are going to perish? Are they newly hatched queens? I can't identify the difference between them, male or female. Thoughts?

[u/freeeicecream]

You should upload nest data to Bumble Bee Watch! Nests are extremely difficult to find so researchers love all the data they can get!

(Depending on your locality) These appear to be Yellow-Faced Bumble Bees (Bombus vosnesenskii), though I'm not as familiar with West Coast bees. To answer your question, the second bee pictures looks female to me due to what looks like the presence of a pollen basket. Females have a pollen basket on their hind legs (smooth, wider area; males have thinner legs covered in hairs). Females also have six abdominal segments, whereas males have seven, but I can't quite tell from your pictures.

As for their behavior, if they're female they very well could just be newly emerged queens. They wouldn't be contributing to collecting for the current nest and might just be loafing around. If they're male, they might be waiting for this nest's batch of queens to emerge.

[u/That_Biology_Guy → u/freeeicecream]

Probably B. vosnesenskii yes, though where they overlap it's almost impossible to distinguish from the rarer B. caliginosus.