Cantharidin, a monoterpene anhydride, is a famous defensive compound produced by the beetles belonging to the families Meloidae and Oedemeridae. Other groups of insects also use cantharidin in chemical defence or communication. These insects are attracted to cantharidin itself or some related compounds. The traps with cantharidin are, therefore, effective to collect these insects; that is a cantharidin world. In this study, such a cantharidin world was investigated by using this type of trap at central Japan. It included the arthropods of the coleopteran families, Anthicidae, Endomychidae, Pyrochroidae, Staphylinidae and Scarabaeidae, the dipteran family Ceratopogonidae, and the opiliones family Podoctidae. In the beetles of Anthicidae, Endomychidae and Pyrochroidae, males were generally attracted to the traps, whereas in the biting midges of Ceratopogonidae (males never feed), only females were attracted, suggesting that the former insects use cantharidin as pheromones to mate, and the latter use it to search hosts to suck. In the other groups, both males and females gathered to the traps although the reasons to be attracted are still unknown. This peculiar community interacted to each other with cantharidin may offer good opportunity to examine the indirect effects between apparently non-related species.