Tuesday, July 5, 2016

A Message From Assateague Island National Seashore

If you’ve been to the seashore in MD lately, it likely that you drove by a few patches of common milkweed on your way in. (We have a HUGE patch growing on the east end of the visitor center parking lot!) Common milkweed is a native plant that is found throughout the US east of the Rocky Mountains. Insects such as bees, wasps, flies, skippers, butterflies and moths visit these beautiful blooms to gather nectar and pollen; however, the plant’s most famous visitor is not interested in the flowers at all.

Over the course of two to five weeks, a monarch butterfly will lay an average of about 700 eggs on the leaves and stem of the milkweed. But why lay eggs on milkweed? Why not pick another host plant? Milkweed leaves which contain a white sap that is loaded with naturally occurring steroids called cardenolides or cardiac glycosides; these chemicals interfere with the heart’s ability to properly function. Even though there is evidence to suggest that the caterpillars themselves may be affected by the toxins they consume as they eat the leaves, as they do so, they become toxic to potential predators.

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