From Ohio History Central
Monarchs (Danaus plexippus) are one of the most recognizable butterflies in Ohio. They are found in every county in the state. With an adult wingspan reaching three and three-eighths to four and seven-eighths inches long, the uppersides of males are bright orange with wide black borders and black veins; the uppersides of females are brown with wide black borders and blurred black veins. Both males and females have white spots on their borders and apex.
Typical monarch habitat includes open areas including fields, meadows, weedy areas, marshes and roadsides
The mass migration of monarchs has been well documented. Millions of monarchs will fly thousands of miles between August and October to winter in Mexico. Once they have arrived at their wintering grounds, the monarchs will feed on nectar during the day, sunning themselves with their wings open toward the sun, and roosting by the millions in trees at night. During the winter of 1996-97, an estimated 160 million monarchs made the journey
There are several generations of monarchs each year. One generation of adult monarchs mate in their winter grounds and the females lay eggs. The second generation migrates north. Once at their northern destination this generation will mate and lay eggs. The third generation spends the summer in Ohio. They will mate and lay eggs creating a new generation that will migrate south. The cycle then repeats. Female monarchs lay eggs, one at a time, on the underneath side of the milkweed leaf. The large, yellow, white, and black striped caterpillars eat the leaves and the flower of the milkweed. The metamorphosis of the monarch from egg to adult takes about a month to complete. An adult monarch that migrates has a life span of six to nine months.
Adult monarchs feed primarily on milkweed nectar, but will visit lilac, red clover and thistle plants. Milkweed is vital to the existence of monarchs. Milkweed contains substances known as cardiac glycosides, a poison. When monarch caterpillars and adults feed on the milkweed, this poison is stored within their bodies. If a predator were to try to eat a monarch, they would have a very unpleasant taste in their mouth. As a result, whenever the predator sees the colors and markings of either the caterpillar or adult monarch, it will remember the bad taste and stay away. A butterfly that looks a lot like the monarch, the viceroy, also benefits from this, even though the viceroy is edible. Although millions of monarchs make the yearly migration to Mexico, the overall population of the popular butterfly has been dropping because of the increase use of pesticides and changing weather patterns in the United States and Mexico.
The Ohio Department of Natural Resource's Maumee Bay State Park has a Monarch Butterfly Research Project underway. The main goal of the project is to increase the chances for the monarch's survival. Monarch caterpillars and eggs have been brought into the center to complete their cycles of metamorphosis. A captive breeding program has also been started. Over 10,000 monarchs have been raised and released at Maumee Bay.