Many pests around us. For example ladybug. These animals are often seen by us.
And we are prejudiced against him. We consider this small animal to disturb the plant. Look, the existence of the grass just does not damage the grass. It's sharp feet can hold on to the twig of the grass, and do not hurt.
However, at a glance we suspect this pest will disrupt the plant. But on the other hand we can see that these animals prey on other organisms, such as lice. Lice that live as parasites in plant leaves. So ladybug preyed on the lice. So, there are biological control measures there. Animals that one prey on other animals, which disrupt the plant.