Notice the flowering plant in the lower right corner of the picture. Here's a closeup of one of the flowers.
This plant is a variety of milkweed named Antelope Horns. Milkweed is essential to the life of Monarch butterflies. The butterfly and the plant evolved together over the centuries. Caterpillars eat only milkweed leaves. Adult monarch butterflies eat nectar from flowers, which consists of about 20% sugar. The chemicals in milkweed protect the monarch. The chemicals the caterpillar ingests remain in its body, even after metamorphosis, making the adult butterfly toxic and bitter-tasting to many predators.
Monarchs migrate to warmer climes for the winter from their winter homes in South America and Mexico, a round-trip of about 6,000 miles. It takes them up to two months to travel each leg of the journey. Each butterfly only makes the trip once, and then its great-grandchildren make the trip the following year.
However, Monarch populations are declining at an alarming rate. The North American monarch population has declined by 90 percent over the past two decades. The decline has been linked to a deadly combination of factors that includes illegal logging in Mexico, wildfires, droughts, and loss of their crucial milkweed habitat in the United States.
Milkweed is in drastic decline due to the human battle against weeds led by the increased use of glyphosate-based herbicides. These are used on genetically modified crops and have been a leading cause of milkweed loss. In fact, this study points to a 58 percent decline of milkweed in the Midwest and an 81 percent decline in monarchs in the Midwest from 1999 to 2010. These declines coincide with increased use of these herbicides.
More information can be found about the plight of Monarch butterflies in the following National Geographic article: National Geographic News