 Among the many irritant and toxic chemicals found in these secretions are alkaloids, benzoquinones, phenols, terpenoids, and hydrogen cyanide.Some of these substances are caustic and can burn the exoskeleton of ants and other insect predators, and the skin and eyes of larger predators.Primates such as capuchin monkeys and lemurs have been observed intentionally irritating millipedes in order to rub the chemicals on themselves to repel mosquitoes.