Monarch butterflies store cardiac glycosides, a poison that they ingest during the larval stage when feeding on the leaves of milkweed plants. This posion can be harmful to birds, mammals, reptiles and amphibians. Unfortunately, for the Monarchs, it isn’t harmful to predatory insects such as the dragonfly. Over the years I have seen quite a few Monarchs being eaten by dragonflies. A couple of weeks ago at St. Marks National Wildlife Refuge I saw several Common Green Darners catch and eat Monarchs.