Monarch Butterfly

Devon Mills

Fleming College

The Monarch Butterfly also known as the Danaus plexippus, is one of the most well know and recognized butterflies. The WWF (World Wildlife Fund) currently lists the Monarch’s status as endangered (2019). Herein we will review the monarch’s physical characteristics, outline it’s life history, feeding ecology and preferred foods.

Physical Characteristics

Figure 1: Monarch Butterfly. Photo: Bonnie McBride

Most easily distinguished by its wing colours of orange, black, and white markings.

The “two pairs of brilliant orange-red wings, featuring black veins and white spots along the edges” (WWF, 2019) give them a stained-glass window effect. As would be expected of a butterfly they barely tip the scale at less than half a gram in weight with their wingspan coming in between 7 and 10 cm.

Alternatively, the larvae of the monarch butterfly (caterpillars) have their own unique appearance (see Figure 2). Monarch caterpillars have yellow, black and white stripes. They grow up to 5 cm. When they metamorphize they shed their skin, leaving a chrysalis that is “seafoam green with tiny yellow spots along its edge” (NWF, 2019).

Figure 2: Monarch caterpillar. Photo: Bonnie McBride

Life History

The NWF (National Wildlife Federation) explains that monarchs exclusively lay their eggs on milkweed which then take 3-5 days to hatch. Those larvae then eat the leaves of the milkweed and about 2 weeks later, form a chrysalis. The monarch butterfly emerges 2 weeks later. Typically, monarchs only live for a “few weeks” but the last ones to hatch in summer “can live upward of eight months” (NWF, 2019). The hope of the species will rest on their tiny little shoulders, as it is this 4th and last batch of monarchs that migrates south to Mexico or California for those living west of the Rocky Mountains according to Stafford Mader, L, (2014). It is crucial for the species that they not only survive the migration south, but also the winter itself. They leave those wintering grounds in the spring and migrate back to Canada for the summer beginning the cycle anew (WWF, 2019).

Preferred Food

While not as prolific as bees, monarchs are still pollinators, the importance of which cannot be overstated. Although the Monarch butterfly can feed on the nectar of many flowers such as “echinacea, black-eyed susan, sage, goldenrod, zinnias and dahlias” (WWF, 2019, para. 7), the most important food source for the species is still the milkweed plants. As stated above, the monarch larvae/caterpillars exclusively eat milkweed.  In Milkweed: Medicine of Monarchs and Humans, Lindsay Stafford Mader explains the connection between the steroid compound called cardenoloid, in milkweed and the decreased risk of infection in the larvae and later the natural toxicity of the butterfly that acts as a defense against predators.

The higher the cardenoloid levels in the milkweed the larvae eats, the higher the caterpillar’s chance of survival. Higher consumption of cardolenoid rich milkweed not only helps with survival on an individual basis but directly connects to the survivability of the species itself. This would be from the common association response poisonous prey induce in their would-be predators.


NWF. (2019). Monarch Butterfly. Retrieved October 31, 2019, from

Stafford Mader, L. (2014). MILKWEED: Medicine of Monarchs and Humans. HerbalGram, (101), 38–47. Retrieved from

WWF. (2019). Monarch Butterfly. Retrieved October 06, 2019, from