Mechanical stimulation ( such as by predator attack ) causes `` reflex bleeding '' in both larval and adult ladybird beetles , in which a toxin is put through the joints of the exoskeleton , deterring feeding . Mechanical stimulation ( such as by predator attack ) causes `` reflex bleeding '' in both larval and adult ladybird beetles , in which an alkaloid toxin is exuded through the joints of the exoskeleton , deterring feeding .