These are resin using bees that glue together pebbles or other material to make nests that they attach to a substrate, usually exposed. These species in Florida are members of the Subgenus Dianthidium Cockerell
Body color and entire legs (except anterior forecoxae) ferruginous D. floridiense
Legs black basally, becoming to some degree yellow or ferruginous apically D. curvatum
County Records: Alachua, Collier, Highlands, Martin, Miami-Dade, Monroe, Sarasota
Locations: Gainesville, Sebring
Dates: March - August
Plants: Croton linearis, Gaillardia pulchella, Helianthius annus
County Records: Highlands
Locations: Archbold Biological Station
Dates: March, March - November according to Mitchell
Plants: Bidens, Sabal according to Mitchell. Calamintha ashei
Notes: Older versions of this website grouped D. curvatum and D. floridiense together. Some information with D. curvatum above may apply to D. floridiense. Older photos here labelled Dianthidium curvatum curvatum are of D. floridiense.