Monarch butterflies, recognized for their striking orange and black patterns and impressive migratory journeys, undertake extensive migrations across North America. This feat requires substantial energy and specific dietary needs throughout their distinct life stages. The food sources monarchs rely upon are fundamental to their survival.
What Monarch Caterpillars Consume
Monarch caterpillars have a specialized diet, feeding exclusively on the leaves of milkweed plants (Asclepias genus). Female monarchs lay their eggs specifically on milkweed, making it essential for caterpillar growth and development. Caterpillars consume milkweed, growing significantly and molting their skin five times over approximately two weeks.
Their milkweed diet involves ingesting chemical compounds called cardiac glycosides (cardenolides) from the plant’s sap. Monarch caterpillars tolerate these compounds, which are toxic to most other insects and animals, and store them in their body tissues. This makes the caterpillars, and later the adult butterflies, unpalatable and toxic to many predators, such as birds. Common milkweed (Asclepias syriaca), swamp milkweed (Asclepias incarnata), and butterfly milkweed (Asclepias tuberosa) are examples of host plants.
What Adult Monarchs Consume
Adult monarch butterflies transition to a different diet, primarily feeding on nectar from a wide variety of flowering plants. Nectar, a sugary liquid produced by flowers, is sipped using their long, straw-like proboscis. This carbohydrate-rich food source provides the energy needed for daily activities, including flight, mating, and egg-laying.
Adult monarchs are generalist feeders, visiting many different kinds of flowers for nectar. Common nectar plants include:
Goldenrod (Solidago spp.)
Asters (Symphyotrichum spp.)
Coneflowers (Echinacea spp.)
Zinnias (Zinnia spp.)
They also consume nectar from milkweed flowers. The availability of diverse flowering plants is important for migrating monarchs, as they require abundant nectar to fuel their long journeys.
Diet’s Role in Monarch Life
The distinct diets of monarch caterpillars and adult butterflies play a role in the species’ survival. The caterpillar’s exclusive reliance on milkweed provides both sustenance and protection. The chemical defense developed from milkweed persists into their adult stage. This defense, signaled by their bright warning coloration, helps reduce predation pressure.
The adult monarch’s nectar diet supports their activities, especially their annual migration. Nectar provides the energy for sustained flight over thousands of miles and allows them to build fat reserves for overwintering. Sufficient nectar also fuels their reproductive efforts upon returning to breeding grounds, ensuring the next generation. The availability of both milkweed for larvae and diverse nectar sources for adults is interconnected and important for monarch survival.