Bullfrogs have become a problem in our ecosystem for serveral reasones. First, they eat everything. They eat not only insect but also spawn,fish,and even snake. Second, bullfrogs are very fertile. So essential animals to maintain ecological pyramid has disappearded rapidly. Finally, there is no a natural enemy of the bullfrog in korea. Because they are from Chaina. Nothing can kill the bullfrog in our nature. So we must kill bullfrogs by our hands.