“…The literature on optimal breeding habitat for monarch butterflies is dominated by studies on the potential declines in survival on different host plants (35% of total studies on breeding habitat loss) and the declines in common milkweed (Asclepias syriaca) in agricultural fields (47% of total studies on breeding habitat loss). Controlled laboratory experiments investigated the oviposition tendencies on different host plants and the effect on larval growth (DiTommaso and Losey, 2003;Mattila and Otis, 2003;Yeargan and Allard, 2005;Casagrande and Dacey, 2007;Pocius et al, 2017a,b), except for two studies that found higher oviposition on common and swamp milkweed (A. incarnata, Pocius et al, 2018) and greater numbers of immature larvae on tropical milkweed (A. curassavica; Malcolm and Brower, 1986) relative to other milkweed species. The effect of the loss of milkweed, principally on agricultural plots, was limited principally to field studies (40% of total studies on milkweed loss, Hartzler, 2010;Pleasants and Oberhauser, 2013;Inamine et al, 2016;Kasten et al, 2016;Zaya et al, 2017) and modeling experiments (60% of total studies on milkweed loss) relating overwintering population abundance to milkweed availability (Zalucki and Lammers, 2010;Flockhart et al, 2015;Zalucki et al, 2016;Hunt and Tongen, 2017;Oberhauser et al, 2017;Pleasants, 2017;Thogmartin et al, 2017a,c).…”