Caterpillars of these butterflies appear to prefer plants that produce iridoid glycosides, which are bitter compounds that release a hormone called gastrin that activates the digestive system (i.e. hunger); therefore, iridoid glycoside producing plants stimulate and attract their appetites particularly when found in plants like "Plantago lanceolata". In fact, the presence of these metabolites may trigger oviposition behaviors in female butterflies so that descendant larval bodies may better incorporate iridoid glycosides. Iridoid glycolyside metabolites appear to have a growth-stimulating effect on caterpillars but a growth-reducing effect on predators. Predators like ants, wasps, birds, and small animals prefer to feed on iridoid glycoside poor caterpillars rather than iridoid glycoside rich larvae, potentially due to these effects. Therefore, immunity of "J. coenia" larvae to predators like ants appears to be strongly related to the concentration of iridoid glycosides sequestered in their bodies. However, too much iridoid glycosides in the diet can negatively affect the immune response of these larvae and lead to increased susceptibility to parasitism.