June 28: First Monarch

In a calm between storms, we observed the first Monarch butterfly of the season flitting around the milkweed patch we let grow wild in the office yard. Monarchs depend on milkweed for much of their life cycle. They lay their eggs on the plants, their caterpillars feed almost entirely on milkweed leaves, and their butterflies sip nectar (though not exclusively) from milkweed flowers. 

Because milkweed contains toxic cardenolides in its sap, this diet renders both the caterpillar and the adult insect poisonous. A bird that eats one will throw up. I've seen a merlin catch a Monarch and then immediately spit it out in mid-air, so the bug must have a bitter taste. It's believed that the distinctive orange and black coloring of the adult Monarch, as well as the jaunty black-and-yellow stripes of the caterpillar, are meant to indicate that this creature shouldn't be messed with--along the same lines as the vivid colors of the poison arrow frogs of the Amazon.

The colors also make the Monarch easily recognizable to those of us who might be quickly scanning a yard to see what's blooming and buzzing. We noted a lack of Monarchs at this time last year, when they'd have been laying eggs, and in early fall, when they migrate. The milkweed stands ready. Hopefully it will host a healthy flock (what is a group of butterflies called?) this summer.

Oozing with toxins,
the milkweed awaits visits
from bright butterflies.