The emerald ash borer was discovered in York County (Maine) in 2018. An invasive species, it has destroyed millions of ash trees in the U.S. and Canada since its detection on this continent in 2002, and is considered one of the most destructive forest pests in North America. If you find an emerald ash borer in Sagadahoc County, report it using this form: https://www.maine.gov/dacf/php/caps/EAB/EABreportFORM.shtml?fbclid=IwAR1ko6nINgXUtSY3QzjxshDp0nNdK0diOCRmlQ38ZdqBarbMdI2WsRgw7b0
Note that the emerald ash borer can be confused with the harmless native tiger beetle, another iridescent green beetle about half an inch long. The reporting form has a good comparison of the two, to prevent misidentification.