Diadasia / sunflower Bee
Female Diadasia rinconis on Opuntia, UC Davis Arboretum, Davis, CA. © Sandy Shanks
Female Diadasia on Sphaeralcea ambigua flower. © Rollin Coville
Male Diadasia rinconis on a cactus flower. © Rollin Coville
Common Name: Sunflower Bee
Diadasia species are very hairy bees and can vary widely in appearance, from a uniform buff color over both thorax and abdomen to grey or charcoal, sometimes with distinct bands of paler hair on the abdomen.
The female carries pollen in a brush of specialized hairs, called a scopa, on each hind leg. Diadasia species have distinctively large scopae which, when filled with pollen, resemble shaggy legwarmers.
Most North American Diadasia species are found in the western states, and are typically “oligolectic,” that is, they obtain pollen from a limited range of plants, often within a single genus or family. For Diadasia, these include primarily sunflowers, cacti, or plants in the Mallow or Evening Primrose families. Different Diadasia species are oligolectic for different plant species; i.e. Diadasia that are sunflower specialists do not collect pollen from cactus, and vice versa. A wider range of plants are visited for nectar.
As many of them are specialists of either sunflowers or cacti, Diadasia have earned the common name of sunflower, or sometimes cactus, bee. Mallow bee would also be an appropriate common name for those Diadasia species that are mallow specialists.
Size: Robust, very hairy, small to medium sized bees, 1/4 to 1 inch in length.
Diadasia is a genus of about forty-three species, all restricted to the Americas, and found predominantly in North America. Most of the thirty or so North American Diadasia species occur in the western United States.
Number of species in North America
Late spring to summer
Pollinated Garden Crops Include
Additional Flowers Visited in Natural Areas
Malacothamnus (bush mallow)
Opuntia (prickly pear)