Froghopper bug. Froghopper bug Cercopis vulnerata, on the stem of a dill plant. Froghoppers, the adult form of spittle bugs, have bright markings to make them deliberately conspicuous to predators. Warning (aposematic) colouration indicates that the animal so coloured has built-in defences such as a sting, poisonous or distasteful flesh, or the capacity to strike back in some way. C. vulnerata is inedible to predators. An inexperienced predator will attack and taste this bug, reject its flesh, and be warned in future by the bright colours.