We are planting milkweed plants in our orchard. One form or another of this weed used to grow almost everywhere in North America, but herbicides have just about wiped it out – and along with it much of the Monarch butterfly population.
Plant milkweed and the bright orange and black butterflies show up almost immediately. I don’t know how they find it so quickly. The orchard is organic – no herbicides, no pesticides. Do insects know that? Can they smell poison?
Soon after, the equally colorful Monarch caterpillars appear on the milkweed leaves. Unlike the butterflies that flutter, soar and plummet, tossed about on invisible currents of air – how do they ever manage to migrate in one direction? –the caterpillars eat purposefully, continuously, systematically consuming the leaf in rows of bites--like eating corn on the cob--down one side of the midrib, then the other.
Tiny circus trains on vertical rails, the caterpillars quickly grow long and fat. You would think they would make a tasty meal for birds, but milkweed contains toxic steroids called cardenolides, which make the caterpillars taste bitter. Their bright colors, like neon signs, advertise “Don’t Eat Here.” Most birds won’t touch them, but a few are not bothered by the poison and will readily eat Monarch caterpillars. It is probably an acquired taste.
Monarch butterflies carry the bitter toxin in their bodies, advertising their unpleasant taste, repelling most birds, but again, some species of birds have learned to eat only the parts of the butterfly that contain less of the poison.
Deprived of its basic food source and pummeled by other environmental misfortunes, the Monarch butterfly population has plunged. Only a fraction of them still winter in Mexico. California’s Monarchs are a different bunch. They migrate up and down the coast, and if they find enough refuges, they will survive.
Like bees, the Monarchs are pollinators, but certainly not as plentiful and probably nowhere near as efficient as the industrious bumblebees, but their brilliant colors and crazy flight patterns are a joy to watch.
We can do little to change their increasingly hostile environment beyond our fence. But if these creatures come to us, are we not obliged to offer them asylum?