Bioluminescence is a common feature of the communication and defence of marine organisms, but this phenomenon is highly restricted in the terrestrial biota. Here, we present a geographical distribution of only the third order of luminescent insects--luminescent cockroaches, with all 13 known and/or herein reported new living species (based on deposited specimens). We show that, for the first time, photo-characteristics of three examined species are nearly identical with those of toxic luminescent click beetles, which they mimic. These observations are the evidence for the mimicry by light--a new type of defensive, batesian and interordinal mimicry. Our analysis surprisingly reveals an evolutionary novelty of all living luminescent insects, while in the sea (and possibly in the soil) luminescence is present also phylogenetically in very primitive organisms.