Halteres (; singular halter or haltere) are small knobbed structures found as a pair in some two-winged insects. They're flapped rapidly and function as accelerometers to help the insect maintain stability in flight, analogous to an aircraft's attitude indicator. The halteres evolved from wings. The ancestral insect species had two pairs of wings (like dragonflies and most other flying insect species have). In the Strepsiptera the forewings evolved into halteres, while in the Diptera (flies, mo… (More on Halteres)