The calling songs of the Namibian armoured ground crickets Acanthoplus longipes and Acanthoproctus diadematus were analysed and described for the first time. Some differences in the length of the cuticular file and the number of the teeth of the pars stridens are also described. The different song patterns are related to differences in the autecology of the two species. Both utilise a broad frequency bandwidth, but the rare and endemic Acanthoproctus diadematus, which lives in interdunal areas of the desert, emits lower frequency signals. These consist of a repetitive sequence of very simple echemes. In contrast the widespread and invasive Acanthoplus longipes, which inhabits open grasslands, emits complex sequences of high-frequency diplosyllabic echemes. Other ecological features, related to the songs of the two species, are discussed. Keywords: calling song, stridulatory organ, armoured ground crickets, behavioural.