Scientists are noticing that the numbers of beneficial flying insects like bees, ladybugs, fireflies and butterflies seem to be declining. They can't be certain about what's happening, but possible reasons include habitat loss, insecticide use, the killing of native weeds, single-crop agriculture, invasive species, light pollution, highway traffic and climate change. As Faith Lapidus reports, the potential causes seem to lead back to what humans are doing to the environment.