Monarch Migration

by Ann Barnes

Google Doodle, 1/9/16
Google Doodle, 1/9/16

Today’s Google doodle commemorates the 41st anniversary of the discovery of the Mountain of Butterflies. The Mountain, now protected as the Monarch Butterfly Biosphere Reserve, is located 62 miles northwest of Mexico City. Each winter, millions of Monarchs make their way to colonies in this reserve.

Monarchs overwintering in Mexico. Photo: Wikipedia
Monarchs overwintering in Mexico. Photo: Wikipedia

Canadian scientists Fred and Norah Urquhart began studying the migration of monarchs in 1937. They tagged and released butterflies and recruited citizen scientists to do the same through their organization, the Insect Migration Association. This group, now known as Monarch Watch, is still actively monitoring monarch migration. The Urquharts mapped migration routes from Canada, across the United States, and into Mexico. Ken Brugger and Catalina Aguado, citizen scientists living in Mexico located the Mountain of Butterflies in 1975 after two years of searching in remote parts of Michoacán, Mexico.In 1976, the Urquharts traveled to the area and found a tagged butterfly, confirming that the monarchs really did make the long journey south.

Migration map Credit: www.flightofthebutterflies.com
Migration map
Credit: http://www.flightofthebutterflies.com

Monarchs begin migrating south in September and arrive in Mexico starting in November. The return northward begins in March. Monarchs traveling north live 4-6 weeks, laying eggs on milkweed plants along their route. Monarchs are dependent on milkweed plants as a site to lay their eggs and as the food source for their caterpillars. It takes multiple generations to make the journey north. However, in the fall, one “super generation” of monarchs is able to travel the full southern route. The super generation butterflies enter a state called diapause during migration. They do not mate while traveling and their bodies store more lipids than the generations of butterflies making the northern trip.

Populations of monarch butterflies have decreased in the years since their overwintering sites were discovered. Urbanization, the increase of large scale farms, and the use of herbicides have reduced the habitat for caterpillars and butterflies along their travel routes. Illegal logging in Mexico has also reduced their overwintering habitat. Climate change also threatens the butterflies and their habitats. Gardeners in the US can help by planting milkweed for monarch caterpillars as well as other nectar rich flowers for adult butterflies. Ideas for attracting butterflies can be found in the Extension publication “Butterflies in your Backyard“.

The story of this discovery was published in National Geographic magazine in 1976. A documentary film called “Flight of the Butterflies” was released in 2012. This film is screened at area science museums from time to time.

Want to learn more about attracting, helping, tracking, or studying monarch butterflies?  http://www.monarchwatch.org/ has lots of information for gardeners, teachers, and anyone who would like to participate in citizen science projects to help the monarchs.

see also: https://durhammastergardeners.wordpress.com/2013/12/13/monarch-melacholy/

Swallowtails

by Ann Barnes

Like many gardeners, I try to plant a variety of pollinator-friendly flowering plants in my yard. Swallowtail butterflies are frequent visitors and are favorites of my family. While watching them, we noticed that there seemed to be many differences in the colors and patterns on the swallowtails in our garden, so we decided to do a little research. We found that the butterflies in the garden belonged to two species, and that we could use the patterns on their wings to not only identify the species, but to tell the males from the females. It’s not as tricky as you might think!

The Eastern Tiger Swallowtail (Papilio glaucus), is the state butterfly of North Carolina. It can be found throughout the state, and most people recognize its yellow and black tiger striped color pattern.

butterfly 004 crop

Male Tiger Swallowtails are yellow with four black tiger stripes on the front edge of their wings. Females are dimorphic – some are yellow and black like the males, while others are mostly black. In either case, the female Tiger Swallowtails have blue and orange spots on the hind wings. Males have little to no blue coloration. Note the male (little blue on the lower wings) between two females in the forefront of this photo:

Photo: Debbie Roos, NC Cooperative Extension
Photo: Debbie Roos, NC Cooperative Extension

Upon close inspection, the tiger stripes are still visible on the black form females:

Photo: Debbie Roos, NC Cooperative Extension
Photo: Debbie Roos, NC Cooperative Extension

Tiger Swallowtail caterpillars feed in trees. Tulip poplar, sweet bay magnolia, and wild black cherry are favorite host plants. Early instars of the caterpillars look similar to bird droppings. Because eggs, caterpillars, and chrysalis of Eastern Tiger Swallowtails are located in trees, we may not often see these stages of the life cycle.  There can be three generations of these butterflies in a year, and they can overwinter in the chrysalis stage.

If one species of butterfly with three color patterns wasn’t confusing enough, the black form of the Eastern Tiger Swallowtail resembles another species of swallowtail: the Black Swallowtail (Papilio polyxenes), also known as the Eastern Black Swallowtail.

Patterned with blue, orange, and yellow, male and female Black Swallowtails’ wings look similar from the underside.

photo (84)

On the top side of the wings, female Black Swallowtails have larger blue spots than males, while males have more prominent yellow spots than the female shown in this photo. All Black Swallowtails have an orange spot with a smaller black dot inside of it located on the lower wing, which helps to distinguish this butterfly from the black form of the Eastern Tiger Swallowtail or other members of the swallowtail family.photo (82)

 

Caterpillars are green, yellow, and black. They feed on strong smelling plants, particularly those in the carrot family like dill, fennel, and Queen Anne’s Lace. This plant choice helps to protect them, because chemicals in the plants make the caterpillars less tasty to predators. There can be three generations of these swallowtails in a year.

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The North Regional branch of the Durham County Library is offering a course titled “Raising Monarch and Eastern Black Swallowtail Butterflies” on September 20 from 2-4 PM. Registration is required by September 16. Per the course description, “Lori Carlson will teach you how to raise and care for caterpillars and chrysalises. Each participant will take home a critter box with a host plant and a caterpillar in order to explore the wonder of these emerging creatures.” Register Here

More about attracting butterflies:

http://content.ces.ncsu.edu/butterflies-in-your-backyard.pdf

http://www.ces.ncsu.edu/depts/ent/notes/4H/butterfly8.html

Photos: Ann Barnes unless otherwise credited. For more photos of Eastern Tiger Swallowtails, click here. For more photos of Black Swallowtails, click here.