They were eventually sacrificed to Hera who had used a gadfly and a flood to impede Hercules' progress with them.
Hercules had to deal with several of these during his tenth labor. After slaying the guardians, Hercules then encountered the priest Cacus who stole some. They were eventually sacrificed to Hera who had used a gadfly and a flood to impede Hercules' progress with them. Name, for 10 points, these animals, an example of which is one into which Zeus transformed Io.
Hercules had to deal with several of these during his tenth labor.
{cow}