Monarchs and PA-gathering

[Carl Karasti]

This (below) was posted on Facebook by Humane Gardner (whomever that is) and I'm just passing it along to those here who would like to expand your observations of Monarchs and participate in doing some citizen science.

Carl Karasti

Humane Gardener

With monarch season in full swing, we need your help! Have you ever seen adult monarch butterflies probing a dried or injured leaf, flower or stem and wondered what the heck they're doing? Well, we can tell you: They're gathering alkaloids to use in their defenses! This is a little studied behavior among monarchs, and it's not the same as caterpillars sequestering cardenolides from milkweed. As a first step in learning more about this important part of monarchs' life history, we need your help to identify which plants they rely on for this purpose.

A number of plant families are known to contain these compounds -- known as PAs (pyrrolizidine alkalioids) -- but they aren't all used by monarchs. So far, with the help of our observers across the country, we've documented monarchs going to:

Late boneset (Eupatorium serotinum)

Blue mistflower (Conoclinium coelestinum),

Joe Pye (Eutrochium spp.),

Virginia bluebells (Mertensia viriginica)

Gravelbar brickellbush (Brickellia cylindracea)

Dogfennel (Eupatorium capillifolium)

Joe Pye (Eutrochium spp.)

Marbleseed (Onosmodium molle)

Borage (Borago officinalis)

But we need many more observations! Please be on the lookout for monarchs extending their proboscises onto injured, wilting or dried plants; the plants need to be in a "damaged" or senescing condition before monarchs can detect the compounds. And PA-gathering is likely not an obligatory behavior; monarchs apparently gather PAs when they need it, and they eventually become satiated. Many people probably pass by monarchs doing this but just assume they are perching. But if the butterfly is extending the proboscis onto the plant, please take note and start watching, take videos and photos, and join our iNaturalist page to upload details of your observation: https://www.inaturalist.org/projects/monarch-rx

In advance of presenting at the wonderful International Monarch Science Symposium held by Monarch Watch two weeks ago, I created a new website where you can find more information about this, including research by my collaborator, chemical ecologist Michael Boppré: www.monarchrx.org