Monarch Butterflies Can’t Survive Without Milkweed
Our region’s milkweeds, including the common milkweed (Asclepias syriaca), swamp milkweed (A. incarnata) and butterfly weed (A. tuberosa) are amazingly complex and beautiful plants best known perhaps for their interesting pods, delicately plumed wind-borne seeds, and critical role in the life cycle of the iconic monarch butterfly (Danaus plexippus).
Without milkweeds to exclusively provide monarch caterpillars their only food source from egg to chrysalis, monarch butterflies cannot survive. Sadly, populations of both native milkweeds and monarchs are in precipitous decline across the nation, linked to extensive herbicide use in glyphosate-tolerant (“Roundup-Ready”) genetically-modified corn and soybean fields, aggressive mowing and herbicide use along roadsides, expanded urban development, logging at over-wintering sites, and generalized habitat fragmentation and degradation.
According to www.monarchwatch.org, at least 100 million acres of milkweed and monarch habitat have been lost in the last decade due to the adoption of glyphosate-tolerant crops, while an additional 6,000 acres are lost to development each day (2.2 million acres per year) within the butterfly’s summer breeding grounds. The eastern North American monarch population is now considered critically-imperiled, as described in a recent report from the Xerces Society for Invertebrate Conservation (Jepsen, et.al, 2015). Protection of existing milkweed stands and enhanced propagation and restoration of native populations are key to the survival of this much beloved butterfly.
Please consider creating a monarch waystation in your own backyard (http://monarchwatch.org/waystations.)
Doing so will not only help the monarchs but also support the lives of countless other species as well. Woven deeply within the life webs of hundreds of creatures, milkweeds truly are home to a marvelous menagerie.
Beyond the monarch, lovely nectar-laden, fragrant flowers attract and nourish a diversity of butterflies, moths, native bees, honeybees, wasps, flies, beetles and ants. Along with their sap, leaves and seeds, milkweeds provide food for more than 450 species of insects (http://www.fs.fed.us/wildflowers). Eastern tiger swallowtail, painted lady, mourning cloak, spangled fritillary, sulfur and cabbage white butterflies, plus nocturnal moths, frequent the blossoms. Milkweeds host the larvae of the queen butterfly, dogbane tiger moth, milkweed tussock moth and more (www.XercesSociety.com).
Leaf-feeding beetles, seed-feeding bugs and stem weevils also find forage and food within the plant’s leaves, stems, pods and seeds, while spiders, lacewings, carpenter ants, earwigs and snails find refuge, shade and shelter there. Although the milky latex of Asclepias contains poisonous, heart-stopping cardenolides intended to defend milkweed against hungry plant-chewing herbivores and disease-causing parasites and pathogens, conspicuous red or orange and black insects such as the milkweed beetle, milkweed tussock caterpillar/tiger moth, large and small milkweed bugs, and the beautiful monarch caterpillar have co-evolved tolerance to these toxins and, in fact, receive great benefit from consuming and incorporating milkweed’s defensive chemical concoction within their own tissues. Now toxic to the taste, these insects’ striking orange-and-black or red-and-black “aposematic” patterning alerts potential predators to stay away, and any clueless young bird ignoring the warning will endure projectile vomiting and a sickening lesson to avoid eating such colorful creatures in the future.
While milkweed blossoms attract a variety of visitors, larger insects such as bumblebees, eastern carpenter bees, the domestic honeybee, and wasps are among their most efficient pollinators. Milkweeds are especially valuable in supporting our native northern bees, many of which are threatened by pesticide poisoning and the loss and fragmentation of foraging habitat. Populations of rusty-patched, American, and yellow-banded bumblebees, eastern carpenter bees, and solitary bees such as digger, sweat and leaf-cutter bees all gain strength and sustenance from milkweed’s rich, nutritious nectar. In turn, these bees play critical roles in the pollination of native wildflowers, commercial orchards, and croplands. Milkweeds also attract beneficial predatory wasps and parasitoid insects that attack field and garden pests, including aphids, slugs, mites, whiteflies, mealybugs and thrips, thereby enhancing agricultural and horticultural health and productivity.
Even at the end of its growing season, Asclepias continues to give silky plumed seeds, and tough, remnant stem fibers yield future nesting materials for black-capped chickadees, finches, northern orioles, and other springtime songbirds. And the seeds and sprouts, if allowed to thrive, bring the promise of new life and another marvelous patch of milkweed within the Chautauqua watershed.
Becky Nystrom is a Professor of Biology at Jamestown Community College, a long-time CWC supporter and volunteer and a founding trustee of the CWC. The Chautauqua Watershed Conservancy is a local not-for-profit organization that is dedicated to preserving and enhancing the water quality, scenic beauty and ecological health of the lakes, streams, wetlands and watersheds of the Chautauqua region. For more information, call 664-2166 or visit www.chautauquawatershed.org or find us on Facebook.