Include host plants in your garden to support the complete lifecyle of butterflies! Adult butterflies & moths lay their eggs on plants, known as host plants, and the caterpillars that follow feed on the plant as they grow. Trees tend to "host the most," but numerous butterflies & moths rely on wildflowers, ferns, grasses or shrubs as host for their larval phase. Caterpillars are an important source of food for birds. It takes thousands of caterpillars to raise one brood of chickadees.