Complex sentence: The larvae then winter in the root system of the plants and in March they reemerge as caterpillars, crawl up the plants and feed on the lupine leaves, absorbing the high nectar content that this lupine provides.
Split into simpler sentences: The larvae then winter in the root system of the plants. In March they emerge as caterpillars, crawl up the plants, and feed on the lupine leaves, absorbing the high nectar content that this lupine provides.