Halteres (/hælˈtɪəriːz/; singular halter or haltere) (from Ancient Greek: ἁλτῆρες, hand-held weights to give an impetus in leaping) are a pair of small club-shaped organs on the body of some flying insects that provide information about body rotations during flight. They are present on flies belonging to two orders, Diptera and Strepsiptera. In dipterans, the halteres evolved from a pair of ancestral hindwings, while males of the much smaller strepsiterans (stylops) have halteres evolved from a pair of ancestral forewings.
Halteres oscillate rapidly along with the wings and operate like vibrating structure gyroscopes: any rotation of the plane of oscillation causes a force on the vibrating halteres by the Coriolis effect. The insect detects this force with sensory organs called campaniform sensilla and chordotonal organs located at the base of the halteres and uses this information to interpret and correct its position in space. Halteres provide rapid feedback to the wing-steering muscles, as well as to the muscles responsible for stabilizing the head.