- any of various plants with blue, bottle-shaped flowers, as the cornflower, grape hyacinth, or closed gentian
- any of a genus (Calliphora) of metallic-blue blowflies
- Any of various blowflies of the genus Calliphora that have an iridescent metallic-blue body and make a loud buzzing noise whilst flying.
- A marine jelly of the genus Physalia, which includes Physalia physalis, the Portuguese man-of-war, and Physalia utriculus, the Pacific man-of-war; a man-of-war.
- A cornflower, a plant that grows in grain fields, Centaurea cyanus, with blue flowers resembling bottles.
- A blue ant, Diamma bicolor, native to Australia.