Abstract This paper presents trends in abundance of adults of Cicindela dorsalis dorsalis Say at all known sites along the Chesapeake Bay shoreline from the 1980s and 1990s through 2014 and provides evidence for causes of these trends. This subspecies was listed as Threatened by the U. S. Fish and Wildlife Service in 1990 because of its extirpation from nearly all of its range north of Maryland and the lack of protection of Chesapeake Bay sites. Adult numbers were estimated during the period of peak abundance using the visual index count method at all known sites. Overall, we found large declines at the western shoreline sites in Virginia and one of two in Maryland and an increase in numbers at Virginia eastern shore sites. Numbers at five Calvert County sites peaked at 6,000 to over 11,000 from 1988 to 1992, but declined to less than 800 adults at one remaining site since 2004. Numbers at the two Maryland Eastern Shore sites, Janes and Cedar Islands, peaked in 2002 at 6,094 at Janes Island and over 2,464...