Toshio experimented with Piranha locusts, crossing their genetic structure with silkworms to give them the ability to consume metal. He turned them into a more hostile species and dubbed his creations the Kiseibya. Shimura intended to keep the Kiseibya contained until he could breed them to be unable to consume human flesh, but the arrival of a Dalek attack force forced him to release the Kiseibya early, to feed and breed in his fellow scientists. He reasoned the scientists would die anyway when the Daleks arrived and their deaths would accomplish something this way.
The Kiseibya proved effective against the Daleks. Although vulnerable to most weapons, the speed of their gestation and reproduction, coupled with their ferocity in attack, helped counter that weakness. The Seventh Doctor was unnerved by the similarities of Shimura's and Davros's research. Each created a new race to "save" their own from a prolonged war. Each was unprepared for their creations' unwillingness to obey them. Shimura insisted his creations would stop the Daleks and save mankind, but the name "Kiseibya" meant "parasitic saviour". suggested to the Doctor that Shimura knew what he was doing was ethically conflicted from the beginning.