Parasite.
Nest parasite to be exact.
Formerly in the genus Psithyrus, these bees are now in the genus Bombus, with the rest of the bumble bees. The idea is that they are just bumble bees that have decided that it is easier to invade other bumble bee nests and disable or kill the queen and have the old queen’s daughters do their bidding….easier than doing all that pollen collecting themselves.
This species appears to be associated with B. perplexus and B. rufocinctus, though there is certainly much more to learn and likely additional hosts. This male came from the State College area of Pennsylvania and collected by Laura Russo. Notably outside of the normal range of B. rufocinctus.
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Public Bee Servant, sam droege