In a new paper, former undergraduate, Lewis Greenstein, did a large review of all the publications he could find and compiled a comprehensive list of all the host plants eaten by monarch caterpillars. He classified all hosts as “high performance” or “low performance” and found that the high performance hosts had on average higher cardenolide concentrations than the low performance hosts. Cardenolides (or Cardiac glycosides) are the toxic compounds that monarchs are adapted to consume that make them toxic to predators. Lewis also did an experiment in which he raised monarchs on low performance host plants to measure their survival. Lewis graduated with Honors in 2021 and has spent the last year as a Public Health Entomology Technician with the Illinois Natural History Survey. You can read the paper, which started out as Lewis’ honors thesis, here