By Rita Thiel
This is the time of year when winged lepidopteras—butterflies—metamorphose and take flight.
Among many species of butterflies that lay eggs and emerge on Ocracoke is the monarch, (Danaus plexippus). They can be spotted in fewer or greater numbers all over the island, depending on the time of year and seasonal conditions.
In October and November, Ocracoke is along their flyway path to Mexico and monarchs can be seen along the island. But some have observed that there are fewer seen for the past several years and there is a reason. In recent years, monarch populations have plummeted nationwide from near 1 billion to less than 33 million.
The brooding grounds in Mexico are especially important as this is where the species mate and lay eggs to start again the first annual generation of monarchs, ready for northern migration.
Where the winged adults feed on nectar from a variety of flowers, the larvae (caterpillars) must have the milkweed plant for their food after the eggs hatch.
Following decades of grassland and prairie loss, monarchs face an ever-increasing challenge to find just the right milkweed plant on which to lay their eggs and continue their annual generational hatchings before migrating to Mexico and other brooding grounds for the winter.
Native, or common milkweed (Asclepias syriaca), once plentiful across North America, is the plant monarchs seek–for its larvae to have food to feed on while the eggs hatch on the leaves. But another increasingly popular species of milkweed, the tropical milkweed (Asclepias curassavica), is becoming widely used in home gardens for attracting monarchs.
There is a debate going on in the butterfly research community on whether or not the tropical milkweed is more
harmful than beneficial to the monarchs. One area of research has found that a parasite can be passed on by this plant to the developing larvae, particularly when it grows all year, thus resulting in weakened and fragile offspring.
Another area of debate surrounds possible disruption of the migratory patterns of monarchs caused by the ever-present food supply from the tropical milkweed in the warmer climates of the United States (climatic zones 8 to 10.) Ocracoke is in zones 6 to 7. Research continues on these issues surrounding tropical milkweed.
Well-meaning gardeners in areas where there is a killing frost should have no concerns with planting any species of milkweed, common or tropical, but those in warmer areas should plant the common, or native, milkweed.
By contrast, the black swallowtail butterfly (Papilio polyxenes), another often seen on Ocracoke, prefers parsley, fennel and dill for its larvae to eat. So, planting these can attract egg-laying swallowtails to your yard. Adult swallowtails feed on the nectar of flowering plants.
The Ocracoke Garden Center does not sell milkweed plants, but milkweed can be purchased at off island plant nurseries.