After 17 years underground, Brood X cicadas will emerge from the soil next month—blanketing forests and tree-lined neighborhood streets across the Eastern United States. This once-in-a-generation ecological event is a rare opportunity for George Washington University researchers to study these harmless insects.
John Lill, chair of the Columbian College of Arts and Sciences’ Department of Biological Sciences, researches the ecology and evolution of plant-herbivore interactions. Working with GW postdoctoral scientist Zoe Getman-Pickering and other collaborators, he is looking forward to testing some fundamental hypotheses about how trophic cascades—an ecological phenomenon triggered by the addition or removal of a species in an ecosystem— operate in Eastern forests.
"We will be testing whether the massive pulse of cicada biomass, which will become the 'blue plate special' for an array of insectivorous animals, alters the diets and foraging behaviors of local insectivorous birds,” he said. “We predict that at least some species of common birds will forage less on their typical prey—caterpillars and sawflies that feed on trees—when cicadas are readily available.
"If this 'ecological release' occurs, we predict that more caterpillars and sawflies will survive, resulting in greater amounts of leaf damage and possibly reduced growth of local trees during emergence years."
The team began collecting data on bird predation of caterpillars and leaf damage during the spring and summer of 2020. They will continue data collection this summer, during and after the Brood X emergence, and for several years following the emergence. Dr. Lill hopes this research will fill gaps in scientific understanding of how periodical cicadas impact local communities and ecosystems.
Dr. Lill shared the truth behind several common myths about cicadas, and explained why researchers want to encourage the public to greet the emerging insects with a source of “wonder, delight and curiosity” instead of fear.