Osmia (Osmia) cornutaare bees with a slight metallic blue or blue-green hue. Females sometimes have a metallic bronze shimmer to the abdomen, entirely black or intermixed black and pale hairs on their head and thorax, and reddish-orange hairs on their abdomen (Amiet et al. 2004). Males are as the females with exception that they usually have intermixed white and black hairs on the thorax and face. (Amiet et al. 2004). Female body length is 12–15 mm, and male body length is 11–13 mm (Amiet et al. 2004).
Osmia cornuta may be confused with O. bicornis due to the presence of two projections on the middle leading edge of the clypeus and males with a small notch on the middle front edge of the clypeus (Peters 1978). Osmia cornuta can be differentiated from O. bicornis by the acute T6 in females and rounded T7 in males (Peters 1978; Amiet et al. 2004).
Osmia cornuta phenology is strongly associated with the blooming of fruit trees. Male adults have been recorded in flight from February to May; females fly from March to early June (Amiet et al. 2004).
Osmia cornuta are generalists and have been observed collecting pollen from 13 different plant families. They are important pollinators of fruit trees and plants within the Rosaceae family (Westrich 1989; Amiet et al. 2004; Haider et al. 2013).
Osmia cornuta nests in insect burrows in soil, drilled borings in wooden blocks and pithy stems, hollow stems, crevices/holes in walls and rocks, and empty snail shells (Friese 1923; Westrich 1989; Bosch et al. 1993; Müller et al. 1997). The nest is divided into a series of cells. Cell partitions and nest plugs are constructed out of mud. In large cavities, the cell is comprised almost entirely of mud (Westrich 1989; Müller et al. 1997; Michener 2007).
Osmia cornuta is native to Europe, North Africa, and western Asia (Russo 2016). O. cornuta were most likely intentionally introduced in the 1980s to the U.S. from Spain for commercial pollination, however, their establishment has not been documented (Russo 2016).