The mirid bugs Macrolophus pygmaeus and M. costalis use substrate-borne vibrational signals during pair formation and in male-male interactions as determined by laser vibrometry. The vibrational communication of Macrolophus is more complex than in other mirids, with a signal repertoire composed of two elements, only produced by males, while the females are mute. The 'yelp' signal consists of one or several consecutive brief pulses with harmonic structure and is commonly produced by stationary males before mating, as a key-element of courtship. 'Yelping' is also associated with contacts between males. The 'roar' signal differs from 'yelps' in that it has a broadband frequency pattern, a longer and more variable duration than 'yelping', and is produced by males in association with walking on the leaf. Playback experiments did not affect male vibration emission, but when 'roaring' was used as stimulus, it elicited a significant increase in the time spent walking. We detected significant differences between M. costalis and M. pygmaeus in some spectral parameters of the 'roar' and 'yelp' signals, so these signals could contain species-specific information. We conclude that 'roaring' and 'yelping' vibrational signals are used by Macrolophus in social communication, in particular in the context of mating behavior.