Poisonous Monarch Caterpillar at Raccoon Creek State Park

Monarch caterpillar photographed by Jeff Zablow at Raccoon Creek State Park

This “bug” is one that we have been seeing little of these last weeks, and it’s a sight that grows a little smile at the corners of your mouth. Danaus plexxipus working its way along a Common milkweed leaf, gently eating the leaf in about the same way that some of us work through corn on the cob.

The Asclepias Syriaca milkweed leaf is gently cut and mashed by the caterpillar’s mouth parts. It is digested, except some of its molecules are not broken down. It’s the glycosides that do not get digested (broken-up). They will be stored in the caterpillar’s body, remaining inert in the pupa and then again in the adult Monarch butterfly. Why is that such a big deal? The glycosides and other related molecules that come from the milkweed leaf are very bitter in taste. Birds, flies, wasps, lizards, snakes–any animal foolish enough to capture a Monarch caterpillar or butterfly will hold it for approximately 0.001 seconds and then violently spit it out. That, my readers, is classic Protecia.

That is why I like to photograph Monarch butterflies.  They have beauty, grace, mystery, are native to our land, and their consumption of milkweed almost guarantees that their wings will not show damage. Animals, birds and reptiles know that Monarchs and their caterpillars are like those wiseguys who lived where I did in Brooklyn:  You see them. You know they are there, and yet you avoid them as best you can. They are just way too toxic.

Funny how frequently I am asked about the toxic and poisonous aspect of Monarch butterflies. It fascinates many people, almost as much as the migration of Monarchs does. To my knowledge this subject remains in the realm of researchers and has not been persuasively explained to the masses in layman’s language. Tens of millions of Americans have some awareness of its existence, but few understand.


2 thoughts on “Poisonous Monarch Caterpillar at Raccoon Creek State Park

  1. Jeff, nice shot. I had about a dozen of those in my back yard a couple of years ago. I had to go to the Internet to find out which ones they were. Unfortunately some large birds evidently got them because the next day they were gone. I think I posted a picture on one of them on Facebook..


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