Plant Milkweed and the Monarchs will Come

Posted Tuesday June 9, 2020

Here is a very happy Monarch caterpillar, munching away on his "host plant"--Common Milkweed (Asclepias syriaca).  

Monarch butterflies cannot survive without milkweeds.  Milkweeds are the caterpillars' only food plant.

Milkweed also provides Monarchs with protection from predators.

Milkweed leaves contain cardiac glycoside, a toxin which accumulates in the Monarchs' exoskeletons, making them bad-tasting and poisonous to hungry birds.   

The glycoside interrupts molecular pumps that keep cells healthy.  Through co-evolution with milkweeds, however, Monarchs have developed immunity to these effects.   Through genetic mutations, Monarchs developed molecular pumps unaffected by milkweeds' glycoside.  They carry the toxin but are not affected by it.   

Predators have learned to associate the color orange with bad taste and bad effects.  Monarchs have an extra margin of safety--thanks to milkweed!

Soon this caterpillar will go off to pupate and then turn into a beautiful orange butterfly--which will drink nectar from milkweed flowers, thus pollinating and helping to propagate his essential, helpful plant.

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