The milk of milkweed is a strong drug. Members of the genus Asclepias — named for the Greek god of medicine — contain “powerful heart poisons that can be used to treat congestive heart failure and atrial fibrillation,” according to this article. Crab spiders that feed on milkweed aphids spin erratic webs, turn pink, grow fat to match the flowers. Monarchs, whose caterpillars eat nothing but milkweed leaves, are said to be immune to the effects of the drug, but I wonder. Would you call a three-thousand-mile mass migration normal behavior? And they’re not alone: the large milkweed bug (Oncopeltus fasciatus), too, is a long-distance traveler, migrating hundreds of miles south each fall to escape the frosts, and returning in the spring.
But the nectar is the main attraction. The globular clusters of flowers emit a fragrance that most humans find a little cloying, but insects find irresistible. Common milkweed has pollinators innumerable that arrive by day and by night: honeybees and bumblebees, wasps, flies, butterflies, moths, and skippers. Many who come to drink, of course, are freeloaders, but the pink cups overflow — there’s enough for all.
A large milkweed patch on a sunny day makes me think of a street of saloons in Hollywood’s version of the Old West. The air is electric with danger and desire. While a pair of monarchs circles in graceful courtship, beetles copulate, and sinister assassins lie in wait for their victims. I found a moth swinging dead from a flower by its proboscis, the victim either of an assassin bug — which tends to dispose of its prey in this fashion, after sucking out the juices — or of the milkweed flower itself, which frequently traps insects in the too-narrow grooves of its sexual parts. The milkweed, let’s remember, has its own agenda: by late fall, to begin to release thousands of seeds into the wind on silk parachutes. So right now, it wants to be pollinated. It wants it bad.
dead moth, species unknown (to me, at least)
Once established, a milkweed colony can expand rapidly through rhizomes, growing from just a few plants to half an acre in a few years. Then, too, it can dwindle over the course of a decade, finally disappearing altogether. Currently, our largest patch of common milkweed is at the end of the old field where it extends up to the ridgetop, which therefore — presuming that migrating monarchs ride the wind currents along the ridges to some extent — may be ideally situated to attract the first monarchs north in early summer. This year, I spotted my first monarch on June 17. This particular patch is only a few years old, and seems still to be in the expansion mode, filling in a strip of field between the edge of a maturing deciduous forest and a 30-year-old grove of Norway spruce. A couple of vernal ponds, which can collect water from heavy rains throughout the year, lie a short distance away through the woods, which is also littered with abundant fallen and standing dead trees of several species and in all states of decomposition. In short, the place is a hotspot of local invertebrate biodiversity — an insect Mecca.
I’ve barely begun to explore the teeming life of the milkweed patch, assembling the better photos into a photo set on flickr. As time and light conditions permit, I hope to augment it. In the meantime, here’s a small selection. As usual, my focus is more on aesthetics than science, but I urge anyone with an interest in natural history to read the article I quoted from above, In a Milkweed Patch, by Marcia Bonta (Hi, Mom!). She — unlike me — has done her research.
I have also scrutinized list after list by scientists that are fascinated by all the insects that live, eat, nectar and/or die on common milkweed and each differs in species’ numbers and kinds. So even though scientists have been studying the common milkweed and its visitors for as long as 113 years–beginning with Illinois naturalist Charles Robertson’s pioneering, 25-year study–there is still much more to be learned about these intriguing wildflowers and their inhabitants.