Insects are extremely important for our ecosystem, not only for their incredible diversity, beauty, and services such as pollination, but also because they provide a large amount of the world's biomass. Many creatures, ranging from birds to lizards, eat insects, and those creatures are in turn eaten by others. However, in order for there to be insects, they must have a food source. Many insects are specialists that can only feed on a limited number of plant species, typically plants that they have evolved with over long time periods. In addition to serving as a food source and creating native insect habitat, native plants also tend to be adapted for the local climate, meaning that they tend to require less water and maintenance.
While more insect habitat is ideal, even just one or two native plants can make a difference. To start, find out what plants are native in your area. In Minnesota, some of my favorite native plants are liatris, asters, and of course the 13 different MN-native species of milkweed! It is also important to plant native trees, many of which also serve as a host plant for many insects. When purchasing plants, make sure that the plants haven't been treated with systemic pesticides. For more information on the importance of native plants, check out Douglas Tallamy's book "Bringing Nature Home: How You Can Sustain Wildlife with Native Plants." Good luck and happy planting!
University of Minnesota Monarch Lab