Though some types of catipillars are excellent food for bearded dragons (ie silkworms, hornworms (domesticated, not wild ones) butterworms) not all are suitable. Many are toxic to most animals who try and eat them (ie wild hornworms eat tomato and tobacco leaves, which causes a toxin to build up in their bodies which will kill most animals who eat them, except those specially designed to manage such high levels of toxins...bearded dragons and pretty much all pet reptiles I know of, are not able to eat wild hornworms. Domesticated hornworms are fed on a specially designed chow that doens't contain these toxins found in the plants wild ones eat).
Don't give any catapillar from outside to your reptiles untill you identify what species they are and what sorts of food they eat. If the plant contains toxins, then those same toxins will be in the catapiller and most likely make your bearded dragon sick or die. Once you identify each catapiller in your area (or the ones you want to feed) then research them to see if they are toxic to birds or small animals. If they are, most likely they are toxic to reptiles.
Most bright colored catapillars are toxic, also catapillers with stiff hairs/spines/ may be difficult for bearded dragons to eat as well. If there is any doubt or concern a particular catapiller or any other insect, cuold be harmful to your dragon, the safer course of action, is don't feed it to your dragon.
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PHLdyPayne