Pacific beetle mimic cockroach Diploptera punctata sprays a noxious chemical, first from internal pouch on the left side of its body, and then from a pouch on the right, leaving dark spots on indicator paper as scientist pinches its legs in this laboratory demo. A number of insects and other arthropod use chemical defences to deter predators The Pacific beetle mimic cockroach is approximately 25 cm in length and is found in Asia and the Pacific, including Hawaii.