I’m looking forward to when the butterflies – sometimes called “flying flowers” – visit yards and fields once again. One of the most interesting of these is the monarch butterfly, the unusual butterfly that actually migrates, flying all the way from Manitoba to high mountain forests in central Mexico, a distance of nearly 5,000 kilometres. What you may not realize is that the butterflies you see flitting about your garden are not the same ones that spent the winter in Mexico. No individual butterflies make the round trip. They may look exactly the same as the ones you saw last summer, but are actually four generations removed from that – the great-grandchildren of last summer’s butterflies.
Their cycle is a strange one. Monarch butterflies from east of the Rocky Mountains spend their winters in central Mexico in the Mariposa Monarca Biosphere Reserve; the western population overwinters in southern California. The butterflies which have been hibernating in a state of dormancy in Mexico reawaken in late February/early March. They become active, find a mate and begin their flight north and eastward, stopping in Texas or Oklahoma where they lay their eggs and die (late March/April). The eggs are laid on milkweed plants, which is the only thing the caterpillars eat.
This second generation (passing through egg, caterpillar, chrysalis, butterfly) has only a six-to eight-week stage (May to June.) The adult butterflies continue their flight farther north in the U.S. where they mate and die. From there the third generation flies to southern Canada, arriving about late June. They too, have about a six-week cycle ( July-August), going through all four stages and then dying. By late summer or early fall, it is the fourth generation, a hardy one, which does not die. This generation actually lives up to about eight months. Their cycle includes the long flight back to Mexico where they gather in large flocks to hibernate over winter. There they sometimes cover whole groves of oyamel forests (coniferous evergreens.) It is this generation which reawakens to start the whole process over. (This generation thus flies from Manitoba to Mexicoand part of the way back!)
How the butterflies do this is still a mystery. Their flight patterns seem to be inherited. It is assumed to be a combination of directional aids such as the magnetic pull of the earth and the position of the sun.
Another interesting feature of monarchs is that they are poisonous or distasteful to most birds and mammals – perhaps due to the milkweed plant which is eaten by the larvae. This feature acts as a definite protection, as birds seem to recognize that this butterfly is a toxin. However, the poison is concentrated in the abdomen and wings, and a few species of birds have learned to differentiate this. They safely consume the part of the insects that is less toxic.
Recent deforestation in Mexico is threatening the survival of the monarch butterfly there. Because the butterflies concentrate in just a few areas, they are particularly vulnerable. Hopefully this trend can be reversed, but the numbers observed in 2010 in Canada and the northern U.S. were much lower than previous years. Some organizations have classed the monarch butterfly as endangered.
Canadians can do their part by helping to provide suitable habitat during the summer.
Do you have room in your backyard for a butterfly garden? Milkweed plants are essential in the life cycle of the monarch butterfly at the larvae stage, but are often too invasive for a garden. Indeed, the wild milkweed has been declared a noxious weed in some parts of Canada, including Manitoba. This doesn’t bode well for the monarch larvae. There are, however, other varieties of milkweed which the monarch larvae can eat.
Adult monarchs, on the other hand, feed on a variety of flowers and fruit tree blossoms, as well as herbs such as mint, and many wild flowers, including asters, wild bergamont, goldenrod and brown-eyed Susans. Planting varieties that bloom at different times will work best. The monarchs will also drink nectar from mushy slices of bananas, oranges and watermelons, if you put these out. There are special butterfly feeders which can be used to offer nectar, and butterfly houses which keep birds out but offer protection from wind and weather, or a shelter at night. I haven’t used any of these yet, but I do hope to provide a variety of plants that will help the monarch butterfly. We all need to try to save this unique insect.
– Donna Gamache writes from MacGregor, Manitoba