Which feature is absent in the female B. flavidus due to parasitism?
The corbicula (pollen-collecting basket)
A defining physical manifestation of the female Yellowish Cuckoo Bumblebee's specialized lifestyle as a social parasite is the complete absence of the corbicula, which functions as a pollen-collecting basket on her hind legs. Unlike most other members of the *Bombus* genus, which possess this structure for gathering pollen and nectar to provision their own colonies, the female *B. flavidus* does not gather pollen. This absence directly stems from its ecological strategy: it relies entirely on infiltrating the established nest of a host species, such as *Bombus terricola* or *Bombus impatiens*, to have its young provisioned by host workers. Observing a large, queen-like bumblebee in the summer nesting season without pollen loads on her legs is a significant field indicator suggesting the presence of a cuckoo species like *B. flavidus*.
