The Monarch Butterfly

WHAT WETLANDS PARK BUTTERFLY IS ALWAYS “DRESSED” FOR HALLOWEEN?

The orange and black colors of the large, beautiful Monarch (Danaus plexippus) butterflies we see at Clark County Wetlands Park are really, really, not Halloween costumes, though the colors are certainly right! These flying beauties are easy to spot, with their upper wing sections colored bright orange and divided by black veins. A sprinkling of white spots ringed in black decorate the black wing edges, and male monarchs have two black glands resembling small, raised dots on their hindwings near the abdomen.

In a world where many creatures depend upon blending into their surroundings for protection, the monarch uses the opposite strategy. Its bright colors stand out in a crowd and advertise to possible predators in search of a meal that this meal will taste terrible. Not just the taste is bad – adult Monarchs contain toxic chemicals known as cardenolides that they absorb and store in their bodies as larvae from the milkweed plants they eat. Even butterflies in their chrysalis stage are protected by these chemicals.  The monarchs’ orange and black colors are clear signals to birds and insect predators alike, saying “I TASTE BAD” and “LEAVE ME ALONE!!!”

Monarch butterflies are probably most famous for their annual multigenerational migrations. The butterflies that breed east of the Rocky Mountains leave their northern breeding grounds between August and October to avoid winter frost. They fly 2,500 to 3,000 miles south, traveling 50 to as much as 100 miles in a single day, enroute to  a small overwintering area in the mountain fir forests of central Mexico. Those that breed west of the Rockies (like the monarchs at Wetlands Park in Clark County, Nevada) travel instead hundreds of miles south and west to specific woodland wintering sites along the California coast from Sonoma in the north to Ensenada, Baja California in the south.

The generation of monarchs that completes the long fall migration lives through the winter and begins the first leg of the spring migration north the following year. These individual butterflies live much longer (up to eight months) than the two or three other generations that complete the spring migration (two to six weeks each).

These migrations are amazing journeys for such small insects, with wingspans just under four inches and weighing less than an ounce each, especially since the individual butterflies in later generations of the spring migration and those making the long journey south have never been where they are going before they make the trip! They are thought to navigate directionally using the position of the sun and the Earth’s magnetic field, but exactly how they do it is unknown. This is a riddle to be solved by future entomologists – anyone want a scientific challenge?

Monarch butterflies are threatened by habitat loss in their overwintering sites, and by development that limits the somewhat disturbed soil areas where host milkweed species grow best. They are also easily poisoned by pesticides used in agriculture, and even in urban yards and landscapes. There is evidence of serious declines in monarch populations over the last 20 years. One of the best ways to ensure that Monarch butterflies survive in the future is to plant the species of milkweeds native to your area that feed monarch larvae. Adult Monarchs benefit greatly from gardens including favorite nectar flowers.  Conservation efforts and information can be found through the Monarch Joint Venture, the Xerces Society, and the U.S. federal government’s National Strategy to Promote the Health of Honey Bees and Other Pollinators.

Habitats favored by monarch butterflies include open fields, roadsides, canyons, and even suburban areas. The butterflies may pause to feed at any habitat that has nectar for them to drink and sheltered places to rest. Favorite native nectar plants for adult monarchs in the Mojave Desert near the Wetlands Park include Blazing Star, Desert Sage, Asters, Goldenrods, Sunflowers, Rabbitbrush, Dogbane, and Western Yarrow. But monarchs breed only on very specific “host” plants – milkweeds in the genus Asclepias. Two Mojave Desert milkweeds, Showy milkweed (Asclepias speciosa) and Narrowleaf milkweed (Asclepias fascicularus) as well as non-native milkweeds fill the bill!

Watch along the trails as you walk at Clark County Wetlands Park for flying monarchs. Their vivid orange and black colors and their soaring pattern of flight, often with their wings held aloft in a “V” shape, make them easy to see!                                                                                                                                                                                                                  

-By Chris Leavitt, President; photos: Anne Marie Lardeau, Secretary

Please enjoy these YouTube videos!

Watch a Breathtaking Monarch Butterfly Swarm, PBS Nature        3:07

Inside the monarch butterfly migration mystery: flying to Mexico from Canada, the U.S.