Great Lakes populations of the bog buckmoth, Hemileuca sp., have been recorded regularly on unusual host plants including purple loosestrife, Lythrum salicaria, suggesting that these populations are unique and possibly deserve protected status. In 2003, a large population of these moths was observed on Lythrum in Wisconsin, with densities of late-instar larvae reaching as high as 40 caterpillars/m². Caterpillar damage resulted in an average reduction of 30% in leaf number and biomass by late summer. An experiment that manipulated caterpillar densities found that herbivory could decrease seed production (as measured by seed capsule number and mass) by 60-80%, suggesting that there is great potential for impact on plant fitness.