Monarch Butterfly
Declining habitat - the milkweed of fencerows and roadsides - adversely affects this insect locally. Illegal logging and human encroachment near the Monarch's overwintering sites in Michoacan have resulted in vast die-offs.
Special
Species
Monarch Butterfly
(Danaus plexippus)
Athough severely hampered by habitat destruction, including the eradication of Milkweed from remaining fencerows and roadsides as well as destruction of overwintering forests, every summer the Busseron Creek Watershed is treated to the sight of the Monarch Butterfly.
Rarely do we see Monarchs earlier than late July, because unlike most other insect species, this butterfly does not overwinter as an egg or pupa. Instead, this butterfly has ties to Central Mexico.
In the warming days of March, the butterflies set out from the Western slopes of the Sierra Madre mountain range of Michoacan, Mexico.
As the insects journey northward, they seek out members of the milkweed family (Ascelpias spp), including the Common Milkweed of Indiana roadsides and the Butterfly Weed of our backyard gardens. As they host much of the life-cycle of this butterfly, these milkweed plants are critical to the survival of Monarch butterflies.
Egg
The adult butterfly will lay up to 500 eggs - a single egg at a time - on the underside of milkweed leaves. Those eggs will hatch after an incubation period of approximately 4 days.
Larva
The newly hatched larvae, or caterpillars, feed on the leaves and stems of the milkweed. The compounds contained in the plant’s leaves and stems of most Asclepias species are toxic to plant-eating animals if consumed. These same toxins are stored by the Monarch, rendering it poisonous to many potential predators. During it’s two-week larval period, the caterpillar eats nearly constantly, multiplying in size and molting 5 separate times - often consuming its dead skin before resuming its feast.
Pupa
When ready to pupate, the caterpillar will seek out a sturdy, sheltering support from which it will suspend by its rear legs. The insect will form a green chrysalis (technically not a cocoon, because it does not have a silken covering) flecked with gold. Over the next 10 days, the final transformation into a regal butterfly occurs.
Adult
At the age of 3 to 8 days, the adult butterfly will mate. Male and female remain together from one afternoon until early the next morning – up to 16 hours. Females begin laying eggs immediately after their first mating, and both sexes can mate several times during their lives. The summer generations of monarchs may live just a few weeks as an adult.
Migration
It takes 3 to 4 generations to reach the Monarch’s most northern summer homes in Canada. The butterflies we see in July and August are actually the 2nd or 3rd generation of the season. The final generation lives longer (possibly over 135 days) and is non-reproductive until the following spring. This last generation’s mission is to travel up to 3000 miles to the mountains of Michoacan, Mexico where the will overwinter. Traveling at an average speed of 12 miles per hour, the butterflies will cover about 50 miles per day. In early to mid-September, you may see flocks of the orange insects as they flutter southward or in masses of 10s and 100s as they rest in the branches of trees during evening hours.
Video - Ecolife / Bill Toone
Overwintering
By November 1st, thousands upon thousands of Monarch butterflies will reach their wintering destination, creating a living carpet over trees and rocks and shrubs. Branches will often collapse under their collective weight. Sadly, deforestation has taken its toll. Over the years as one tree at a time has been felled for heating and cooking fuel, the microclimates of the region have changed. The massed butterflies are often unprotected from cold weather and die. The mounds of Monarchs in the video above - are dead.
Still the cycle continues. Each spring, the now-reproductive final generation becomes the first generation to begin the trek again.