If they jump, they are springtails. If the crawl, they are mites. Mites normally do not pose a threat to frogs or toads, but I would feel uncomfortable if there were a large number and if they covered the frogs! EEEK! Could they possibly be traveling in with your feeders? Do you farm your own mealworms? If so, and depending on what you are using as their bedding, they could be grain mites, which are a real pain in the a$$!