Communicative behaviour of nine species of Australian grasshoppers (seven Oedipodinae and two Gomphocerinae) is described and compared to North American and European species. Most signal types are represented in all three continents. Most similarities between the three groups are probably due to the retention of characteristics present in common ancestors. Other similarities evidently are convergent (i.e. arose independently in each continent); these include: (1) loss of femoro-tegminal stridulation in several species; (2) changes in the function of signals from one communicative context to another; (3) the ritualization of kicking movements (i.e. the evolution of signals from non-communicative kicking movements) ; (4) the evolution of specialized flight sounds in the Gomphocerinae. Female attracting flight displays are performed by relatively few Australian Oedipodinae. Characteristics of an individual that are closely associated with behaviour or physiological states of that individual and that are relevant to the activities or wellbeing of other individuals have a greater probability of becoming signals (becoming ritualized) than movements that occur in many situations (i.e. that are unpredictable).