They are named from their habit of making compartments of mud in their nests, which are made in hollow reeds or holes in wood made by wood-boring insects. It is a tremendous pollinator, calculated to be between 120 and 200 times more efficient than the honey bee. Like many solitary bees, it doesn’t have pollen sacs, so most of the sticky pollen is deposited on the furry underside of its body. Whenever these swiftly moving bees enter a flower, pollen is transferred to the next, and so on . . .

Ostia species are usually metallic green or blue, though many are blackish. Most have black ventral scope which are difficult to notice unless laden with pollen.

Males are the first to emerge, the females will appear in a week or two later by which time the males will be ready and waiting to mate.