Insects on a leaf

Add a few insects and bugs, lady bugs, bees, butterflies, worms, slugs, dragon flies, eggs, earwigs etc to a leaf. A great project for Earth Day after observing life close up in the garden, by a pond or in the woods.
Summer is the time for seeing large numbers of many of these in the garden, some friends like the lady bug and some pests like the earwig and slug.
How do we face the challenge of these tiny but big crop destroyers without harming our planet?