The present study focuses on flower visitors and pollinators of some globular cacti and opuntias of the southwestern USA. Flowers of these cacti are predominantly melittophilous, and medium-sized to large bees are their most important and most efficient pollinators. A brief summary of the most common bee genera visiting cactus flowers in southwestern USA is given. Other common visitors of the cactus flowers are nitidulid beetles that are very poor pollinators and can be considered pollen thieves. Two other unexpected cactus flower visitors were identified during this study: true flies of the genus Triploechus from Pediocactus bradyi flowers and hawk moth (Hyles lineata) from a flower of Echinomastus johnsonii.