Katydids make sound by stridulating i.e. rubbing their forewings together. Males of various species can be differentiated acoustically. Each has a unique calling pattern and during the mating season groups of males sing in unison. Females of Gampsocleis glabra select males on the basis of relative signal timing in duets rather than by evaluating other signal properties. Temperatures affect the acoustic behaviour and song traits. With a temperature drop the stridulation slows down proportionally, until 11°C when G. glabra is no longer heard.