Rock Buckwheat or, Round-headed Buckwheat
Eriogonum species are used as food plants by the larvae of some
Lepidoptera (butterflies and moths). Several of these are monophagous, meaning their
caterpillars only feed on this genus, sometimes just on a single taxon of Eriogonum.
Wild buckwheat flowers are also an important source of food for these and other Lepidoptera.
In some cases, the relationship is so close that
Eriogonum and dependent Lepidoptera are in danger of coextinction. (from Wikipedia)