With winter’s arrival, invasive species may be out of sight and out of mind. They always seem to come back each year — where do they go in winter? Researchers are investigating how invasive species behave and how they are equipped to survive winter and reemerge when temperatures warm. Some invasive species are particularly adapted to survive cold northern winters. Recent research has been done to understand the overwintering behavior of the emerald ash borer (EAB), a metallic-green wood-boring beetle native to East Asia. All species of North American ash trees are vulnerable to the beetle, which has killed millions of trees in both forested and urban areas in the United States. EAB larvae overwinter under the bark of ash trees. Windchill does not affect them, as the bark provides protection. EAB larvae synthesize antifreeze agents internally in the fall to survive winter. The peak of their cold tolerance is January and February. A cold snap in late fall or early spring (when they are not fully acclimatized) may have a greater impact on EAB survival than sustained cold temperatures midwinter. As the severity of winters changes due to the Climate Crisis, more invasive species may be able to survive, increasing the need for greater prevention and control measures; for example, throughout the year, firewood should be sourced in the same area where it will be burned.