Eureka red weed seeds
The caterpillars of most butterfly and moth species have evolved to eat the leaves of just a small number of plant species native to their geographic range, sometimes in just one genus of plants. These plants are called "host plants" for that species of butterfly or moth. If a given species of butterfly or moth cant find their particular host plants in an area, it will die out in that area.
Non-native plants can seldom be host plants for native butterfly or moth species. Butterflies often have preferences for native nectar sources, but they can usually make do with non-native nectar. However, 90% of caterpillar species cant get past the chemical and structural defenses of other than a handful of native plants with which they coevolved. This is the primary reason why native landscapes support 35x more caterpillar biomass than non-native landscapes.
Native plants and caterpillars are a key foundation of our whole native ecosystem. Terrestrial birds, predator/beneficial insects and a large part of the rest of the food chain depend either directly or indirectly on native plant – caterpillar pairs. For example, 96% of terrestrial bird species rely on insects to feed their young, and fat juicy caterpillars are the most important part of that diet. So if the required native plants are not present in an area, nearly all butterfly and moth species will die out in that area along with much of the other animal life that depends on them.
So grow host plants for your native butterflies and moths and help restore nature one garden at a time! For more information, read "Plant Choice Matters", excerpted from "Nature's Best Hope" by University of Delaware Professor of Entomology Doug Tallamy.