Halteres are modified wings. In the Diptera (true flies) it is the hind wings that have become halteres.

Which insects have halteres wings?

Examples of insects with halteres are houseflies, mosquitoes, gnats, strepsiptera, and craneflies.

Do Diptera have wings?

All Diptera are equipped with only one pair of functional wings, which are on the mesothorax (front). The wings on the metathorax are transformed into the halteres or rocker arms. From this characteristic comes the name of the order, from the Greek dipteros, which means "two wings".