Insects are Really Important
There is more insect biomass on earth than all other animal species combined, and animals are fundamentally dependent on insects for their food. For example, 96% of eastern terrestrial bird species feed their young the high protein diets that only insects (particularly caterpillars) can provide for rapid development. Insects form the foundation of the food chain for all higher order animals.
Plants Form Important Relationships with Insects
Not all insects can eat all plants, however. All plants develop defenses that keep insects and other animals from eating them into extinction. Most often, these defenses are in the form of chemicals that are either toxic or make the plant unpalatable. Because native plants and native insects have co-evolved over millennia, insect-plant relationships have co-evolved such that 90% of insect species specialize on just one or a few species of plants.
For example, native Milkweed has a toxic chemical in its sap that makes it unpalatable to most insect species, Monarch caterpillars being one of just a few dozen exceptions. And, Monarch caterpillars can only eat Milkweeds so if Milkweeds were to disappear there would be no Monarchs.
Using Alien Plant Species Condemns Insects to Starvation
Introduced alien plants which are not native to our region have chemical defenses that our local insects have not had enough evolutionary time to overcome. Because most of our urban and suburban landscapes are filled (sometimes exclusively) with alien plant species there is little food available for insects and the animals that eat them. Therefore, we are literally condemning insects and the animals up the food chain to starvation.