Although chorusing behaviour has been reported previously in six species of corixid water bugs, including one European species ofMicronecta, no analysis of chorusing has been published forMicronecta.Studies of a large pond in SE Australia show that chorusing occurred in the most common species ofMicronectain the study area,M. concordia.Pulse-trains synchronized with those of other individuals nearby were the predominant acoustic output ofM. concordiamales throughout the stridulating season, from mid-winter to mid-summer. At the start of the season, chorusing began with an exponential increase in the percentage of synchronized signals over a period of six days.