Wisconsin is part of the Upper Midwest spring breeding area for Monarchs. They generally arrive from Mexico in May and June, looking for milkweed to lay hundreds of eggs. The caterpillars developing from the eggs then enjoy the milkweed leaves for their food, building up poison from the milkweed in their system. This poison helps protect them and the cocoon they soon form against ants, spiders, and wasps. The poison later helps the adult Monarch emerging from the cocoon to fend off predators, such as birds.
Cold and wet weather, of course, diminish reproductive success of the Monarch.The early three generations of Monarchs live only six weeks after they emerge from the cocoon. Later generations live up to eight months and can make the trek back the Monarch's hibernation place in Mexico – if they find enough milkweed to feed on the way.
Unfortunately, as we all know, in the monarch migration corridor to the south a large portion of the milkweed habitat has been eliminated – lost to the expanding corn belt and use of agricultural herbicide, as well as development. According to an estimate by the Director of the Monarch Watch at the University of Kansas, 5-15 million milkweed, via planting of seeds and plugs, will be required to offset the habitat losses for milkweed in the monarch migration corridor. Don't forget to pack milkweed seeds when you travel south. Gisela
Gisela Kutzbach and contributors