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Milkweed microhabitat

Milkweed bugs are aptly named, feeding exclusively on milkweed plants. The bright color and pattern advertise the fact that this beetle has stored some of the milkweed’s cardiac glycoside in its body to predators.

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.