Magical Monarchs
BY MADISON HRYSKO, GROUP FOR THE EAST END ENVIRONMENTAL ASSOCIATE
The monarch butterfly (Danaus plexippus) is the only butterfly species to have a two-way migration, similar to many bird species. There are two populations of monarch butterflies in the United States, one to the west of the Rocky Mountains and one to the east. The eastern population of monarchs overwinter in the Sierra Madre Mountains of Mexico, while the western population overwinters on the coast of California. Monarch butterflies migrate because they can’t survive harsh winter conditions in the northern part of their range.
In the spring, monarch butterflies leave the southern part of their range, the Sierra Madre Mountains, to start their journey north. This journey is multigenerational (usually taking 3-4 generations); monarch’s lay eggs along their migration north and it is the subsequent generations that complete the migration. This means the butterflies on Long Island seen in August through October are most likely offspring from the southern generations of monarchs.
Common milkweed
During the monarch’s time on Long Island, they will lay their eggs on milkweed (Asclepiadaceae) plants. Milkweed is a host plant for the monarch, meaning it is the only plant they can eat and the only plant they lay their eggs on. It plays a vital role in the monarch's survival.
As caterpillars, they will store energy from ingesting milkweed. In addition to food and a place to lay eggs, milkweed also provides the monarch butterfly with protection against predators. The toxic nature of milkweed makes the monarch butterfly taste very bad to unknowing predators. If eaten, these predators will become averse to the bright orange butterfly, aiding in the monarchs' protection. Since milkweed is imperative to the monarch's survival, some researchers have begun to call milkweed a more intuitive name like ‘Monarch’s Delight’, because of their symbiotic relationship.
Monarch’s, like other insects, undergo metamorphosis, a significant transformation from egg to caterpillar to chrysalis and finally, a butterfly. This process typically takes about a month. If you look carefully this is a process that can be seen on Long Island!
Source: Butterfly Identification
Adult monarch butterflies have visual differences depending on if the butterfly is male or female. Male monarchs have black spots near the bottom of their wing, while the female does not. The female monarch also has thicker black veins on the wings. On other species of butterflies, the black spots secrete hormones to attract possible mates, but scientists do not know if this is the case for monarch butterflies.
After summering on Long Island, monarch butterflies begin their migration to their wintering grounds in Mexico, usually between September and October. Decreases in temperature and day length are environmental signals to monarchs that it is their time to head to warmer climates. The fall migration differs from the spring migration because it is done in one generation. This migration is not an easy trip, with many monarchs traveling 3,000 miles to get to their overwintering destination, averaging about 50 miles a day!
Monarch caterpillar and butterfly spotted on common milkweed at Downs Farm Preserve in Cutchogue
Downs Farm Preserve in Cutchogue is a great place to explore and search for monarch butterflies. Or plant milkweed in your yard to have a front row seat to the magic of these beautiful monarch butterflies. Carefully check the underside of the milkweed plants to see if you can spot any tiny caterpillar eggs!
https://www.nycgovparks.org/parks/long-island-mews/highlights/11320
https://monarchjointventure.org/monarch-biology/annual-life-cycle