I give these hand stitched caps to people that help me make an impact and bring back the endangered wild bees.
Bombus Affinis, the Rusty Patch Bumble bee was listed as Endangered January 11, 2017.
A great resource for learning about native bees is below.
https://xerces.org/wp-content/uploads/2016/10/2017-009_B-affinis_IDGuide_web.pdf