California Milkweed - Aslepias . California Milkweed Aslepias spp. Although the milky juice is poisonous and wards off most munching or browsing animals, the caterpillars of the Monarch butterfly feed exclusively on milkweed parts, storing the poisons to make themselves vile tasting to birds. Few birds that have tasted these caterpillars return for more.
Milkweeds are also noteworthy for their ornately complex pollination machinery.
Instead of separate stamens, the stamens are fused to the style, but the filaments of these stamens are enlarged into colorful, nectar-bearing cups. At a visit to another flower, the pollinator's leg may chance to rub against one of the five vertical stigmatic slits, and the pollen ball is inserted. Each species has its own special shape for pollen ball and stigma, just like a lock and key.