Which group is solely responsible for feeding the Bombus flavidus larvae once the queen has usurped a host nest?

Host workers

Once a *Bombus flavidus* queen successfully invades and takes over a nascent colony of a host species, such as *B. rufocinctus* or *B. perplexus*, the responsibility for feeding the parasitic brood falls entirely upon the existing host workers. These host workers transition their provisioning duties from feeding their own developing brood to feeding the eggs and subsequent larvae laid by the invading *B. flavidus* queen. This outsourcing of labor is fundamental to the cuckoo strategy. The *B. flavidus* queen only needs to secure nectar for her own immediate energy needs, allowing her to focus energy on territorial monitoring or dominance assertion, rather than undertaking the laborious, long-haul flights required to gather the pollen necessary for larval growth.