Diadasia rinconis, right, Pima Co., AZ_2016-09-30-17.55
Diadasia rinconis is a cactus bee that is primarily found in the mountains and deserts of the southwestern U. S. and south into Mexico (1). Yellowstone is as far north as this bee has been recorded in the U. S., with only one other record from Alberta, Canada (1). D. rinconis are solitary bees and form individual nests in bare, open patches of ground (2). Though solitary, they nest in close proximity to one another forming large, dense aggregations (2). Males fly en masse low to the ground among these vast nest sites, awaiting females going into or out of nest entrances (somewhat like a game of “Whack-A-Mole”… but with bees) (2). When a female appears, multiple males immediately pounce on her in an attempt to mate, and form a rolling, writhing “mating ball” (2). Diadasia in the western U. S. are cactus specialists, inhabiting montane meadows and open, arid, grassy areas (3). They will visit various families of flowers for nectar, but collect pollen for their young from Cactaceae (cactus), especially Opuntia (Prickly Pears) (1). Original public domain image from Flickr