design: Feces (or controls) extracted with QIAamp PowerFecal DNA kits and processed for sequencing at the DNA Service Facility at the University of Illinois-Chicago to amplify part of the COI region using modified ZBJ primers developed by Zeale et al (doi: 10.1111/j.1755-0998.2010.02920.x). Primers were modified to match the monarch COI sequence (Forward: RGATATTGGWACWTTATATTTTATTTTTGG, Reverse as per Zeale et al. 2011).