Calyptratae flies lacking these knobby structures took a lot longer to become airborne, but takeoff time wasn't affected in non-Calyptratae flies without halteres.

First fossil of an oestroid fly (Diptera: Calyptratae: Oestroidea) and the dating of oestroid divergence. PLoS ONE , 2017 DOI: 10.1371/journal.pone.0182101 Cite This Page : ...

A group of flies known as Calyptratae, which includes houseflies and blowflies, rhythmically move these wings when standing. “We know that they’re the only group that does this,” says Yarger.