It is the Monarch's exclusive food source for their larvae.
The monarch butterfly? They eat milkweed.
The viceroy butterfly does not eat milkweed, it is a mimic of the monarch butterfly which does eat milkweed. The milkweed makes the monarch butterfly toxic to birds. Once a bird eats its first monarch butterfly it gets so sick that it learns to never try to eat anything that looks like a monarch butterfly ever again. The viceroy butterfly has evolved to mimic the monarch butterfly to avoid being eaten by birds that have previously tried eating a monarch butterfly.
Milkweed.
The monarch butterfly migrates to Mexico for the winter.
The role of a monarch butterfly is to keep the milkweed population controlled
The monarch butterfly produces a chemical that gives its body a very bitter taste; which birds hate. They get that taste from the Milkweed plant which they feed on. These are the adaptations of the Monarch butterfly and it benefits by feeding on the milkweed plant and stays safe.
The adaptation of the monarch butterfly is a early diet of milkweed. This diet of milkweed ensures the caterpillars and the adults taste terrible. A predator has only to taste the bitter monarch once to learn to avoid them in the future.
The relationship between monarch caterpillars and milkweed is mutualistic. The monarch caterpillar eats the milkweed.
Danaus plexippus.
milkweed
Monarch butterfly caterpillars primarily feed on milkweed plants. Additionally, some insects like milkweed bugs and beetles also consume various parts of the milkweed plant.
The Monarch butterfly lives in the grassland for a short period, to try to stay warm until it goes to California, then Mexico. The grassland also has many milkweed plants like; the Mexican milkweed, and the Milkweed you see in Texas.