The genus Brachyglossula is specialized in collecting pollen from Cactaceae (see Roig-Alsina & Schlumpberger, 2008)
References
ROIG-ALSINA, A. & SCHLUMPBERGER, B. O. 2008. The cactus-specialist bees of the genus Brachyglossula Hedicke (Hymenoptera: Colletidae): notes on host associations and description of a new species. J. Kansas Entomol. Soc. 81 (2): 84-91