The paper deals with acoustical and chemical aposematic (warning) signals in insects. For this purpose, several species of velvet ants (Hymenoptera: Mutillidae) from South Africa, Europe, and Brazil were investigated by laser vibrometry, sound analysis (e.g. sonagram, cepstrum analysis, and Baraniuk Jones adapted optimal kernel time frequency transformation), and gas chromatography coupled with mass spectrometry. With the help of a new model it is possible to compute the vibration and air borne sound spectra, and to estimate the sound intensities produced by the animals. In the secretions of the mandibular glands several ketones, alcohols, and acetophenone were found. 4-Methyl-3-heptanone occurs in all investigated species. Substances found to have possibly aposematic function in some species are alkylpyrazines and a monoterpenoid. Furthermore, the paper contains a review over all aspects of biology of the family Mutillidae completed by a literature chapter with more than 500 citations.