I observed this butterfly on a hilltop near Albertson Fire Road. The plant it is foraging on is Spanish Clover or Spanish Lotus aka American bird’s foot trefoil, Acmispon americanus, one of several caterpillar host plants for this species. According to Calscape, there are 533 likely host plants for the Acmon Blue, making it a generalist and very adaptable to what is available for laying eggs. A generalist has an easier time finding the resources it needs to feed and reproduce as compared with a specialist, such as the Monarch.
Another generalist that I have seen in my garden and on the trails this spring is the Painted Lady. Several caterpillars hatched on and have been munching on the lupine around my house. Last year the desert superbloom created favorable conditions for a great migration of Painted Lady butterflies. The larvae that developed in the Santa Monica Mountains area mowed down many an invasive thistle that sprung up after the Woolsey Fire. Painted Lady caterpillars make tents out of leaves by stringing leaf edges together and zipping themselves in with their own silk as defense against predators, such as ants.
Specialists like the Monarch lay their eggs only on milkweed and the larvae will not eat anything else. No milkweed, no caterpillars, no reproduction.