I realize the point is moot now, but my own Google search for pain causing a fever led me to multiple answers of NO, and I know from my own medical issues that it is untrue, fever can be a rather rare response of the body to pain.
Harvester ants are the staple food source for most types of Horned Lizards or (horn toads). They provide formic acid - a necessary nutrient for horned lizards. A typical horned lizard adult may eat from 20 - 100 harvester ants a day. However, most pet stores do not supply harvester ants as feeders for horned lizards.
Since toads are carnivores, they prefer to eat insects, worms and other types of live prey. Baby toads are often quite small, especially right after they have undergone metamorphosis from the tadpole stage. That can make it difficult to feed them, though there are a number of insects that baby toads can eat.