September 22, 2011 —
Anyone who has walked in a field or a roadside has probably at one time or another picked a leaf of a milkweed plant and observed its milky sap start to flow from the plant; hence its name. Like all plants, the milkweed contains a myriad of chemical compounds that are used by the plant in various ways.
Among the compounds produced by the milkweed are cardiac glycosides; compounds that are toxic to humans and other vertebrates if eaten. Ingest milkweed and you will probably experience varied symptoms such as nausea, altered mental status, and cardiac-related symptoms such as chest pressure and shortness of breath.
If these compounds are so bad, then why is the milkweed plant a host to a variety of insects? The answer is that many insects are unaffected by glycosides. These insects are actually aided by the milkweed’s toxic offering; the insects’ ingestion of milkweed makes them unpalatable to would-be predators. Like many other toxic creatures, these insects advertise their bad taste by bright colors and patterns. The monarch butterfly and the milkweed plant’s interaction is well known. A host of other insects are also participants in the realm of the milkweed microhabitat.