Going Out

By Ed Wesely

Milkweed village, part II

Last time, I described two beetles that depend on the common milkweed plant—the milkweed longhorn beetle and the milkweed leaf beetle, which restrict their diets to milkweed leaves and which lay eggs on the undersides.

Warning coloration. Somehow both beetles “understand” that milkweed sap contains slightly toxic compounds that make their larvae and ultimately the adults unpalatable to many predators.

By waiving protective camouflage in favor of gaudy red/orange colors mixed with black, they mimic monarch butterflies, which share the same “warning coloration.” “Look out. I taste horrible,” they advise potential enemies.

Milkweed sap contains a family of chemicals related to digitalis, a common heart stimulant. If you’ve handled the sticky white latex that flows from a wound in the plant, you’ve also discovered that it coagulates on exposure to the air.

During World War II we developed ways to manufacture synthetic rubber from milkweed sap, but the process proved too expensive for commercial production.

Harlequin caterpillars. Visitors to a milkweed patch in August and September will regularly encounter hairy orange and black caterpillars, about an inch long—which began life when a parent, the milkweed tussock moth, laid several hundred miniscule eggs beneath a milkweed leaf.

The eggs were covered, as spider eggs often are, with a sheaf of tough, gauzy silk about the size of a fingernail. After a few days an army of tiny white caterpillars emerged to begin feeding, moving from leaf to leaf in tight formation and stripping all but the most durable veins.

After several molts they developed distinctive tufts of orange and black hair, which mimic the colors of other milkweed insects. Decades ago the colors reminded a biologist of old-time harlequin clowns, which led to the name.

As they mature, harlequin caterpillars that escape disease and predation retreat to safe havens under grass and leaves, to fashion cocoons from their own body hairs. Within these shelters, they develop hard, durable cases, which persist through winter.

If all goes well, newly minted tussock moths will emerge in May, to replace adults that perished in autumn frosts.

Pond plant program. On Saturday, August 10, botanist Ann Rhoads will host a 10:00 a.m. program at Duck Harbor Pond in Wayne County to identify pond plants and to explain their roles in pond health. For information and/or directions call 570/729-7053.