The stridulatory organs of male and female Mutillid wasps are similar and occur between their 3rd and 4th abdominal tergites. Previous knowledge of these organs, and of the related behaviour, is limited. For that reason the. stridulatory files of Smicromyrme rufipes, Dasylabris maura, D. kozlovi and Mutilla marginata were investigated by scanning electron microscopy (SEM). Sonagrams of the distress calls of three species were evaluated and compared one with another, and with results obtained by SEM and video analysis. The used novel low-cost equipment for sound recording and analyzing allows sampling rates up to 100 kHz, and it is portable and completely battery-operated. Channel-time spectrograms are possible under field conditions.