Agricultural insecticides were a key factor, according to a study focused on the Midwest, though researchers emphasized the importance of climate change and habitat loss. Agricultural insecticides were a key factor, according to a study focused on the Midwest, though researchers emphasized the importance of climate change and habitat loss. Butterflies and Moths, Pesticides, Research, PLoS One (Journal), Biodiversity, Midwestern States (US), Endangered and Extinct Species, Wildlife Die-Offs, Agriculture and Farming, Land Use Policies, Global Warming NYT > Science