A group of four North American dasytine species is carved from the genus Trichochrous Motschulsky, 1860. The genus Microasydates Gimmel and Mayor, new genus (type species: Pristoscelis umbratus LeConte, 1866) is created for these species. This new genus is clearly defined based on several adult male characters, including the presence of a field of coarse black setae concentrated medially on abdominal ventrite 4, slender tibial spurs in combination with the head not distinctly enlarged, lack of a basal strut on abdominal sternite VIII, tegmen membranous apically, and ventral teeth on the median lobe of the aedeagus. Species are distinguished primarily by characters of pronotal shape, setation, female pygidium, and the median lobe of the male aedeagus. Previously described are Microasydates punctipennis (LeConte, 1866), new combination and Microasydates umbratus (LeConte, 1866), new combination. Newly described are Microasydates sanclemente Gimmel and Mayor, new species and Microasydates santabarbara Gimmel and Mayor, new species. The only widespread mainland species is M. umbratus, which occurs almost throughout California across the Great Basin into Utah, while the remainder of the diversity is in the California Channel Islands and Santa Ynez Mountains in Santa Barbara County. Upon examination of type material, Trichochrous indigens Casey, 1895, Trichochrous nubilatus Casey, 1895, Trichochrous separatus Casey, 1895, Trichochrous suffusus Casey, 1895, Trichochrous testaceus Casey, 1895, and Trichochrous pratensis Blaisdell, 1924 are all considered new junior subjective synonyms of M. umbratus. Trichochrous fulvovestitus Casey, 1895, status restored, and its junior synonym, Trichochrous propinquus Casey, 1895, are removed from synonymy with M. umbratus and retained in the genus Trichochrous. Adults of Microasydates are active during mid to late summer, and aggregate, often in large numbers, on the flowers of a wide variety of mostly perennial plants, where they mate and apparently feed on pollen, nectar, and occasionally small arthropods. Seasonality data and known host plant associations are provided along with species treatments.