The eastern Asian brown marmorated stink bug, Halyomorpha halys (Stål), is a nuisance and a crop pest in many parts of the United States. Mainly reports of citizens that were verified by experts were used to show that the distributional range of H. halys in Connecticut steadily increased from 2008 when it was first discovered until June 2015 when it was generally present throughout the state. The number of sightings (grouped by 12-month periods from 1 July to 30 June of the next year) showed a three-tiered pattern, being low in the first two reporting periods, higher in the next three, and highest in the last two. The number of new towns (local governing units in the state) documented to have H. halys increased from 2008–2009 to 2010–2011, and then generally decreased thereafter. On a diversified farm in Hamden, Connecticut, adults entered an ultraviolet light-trap during eight weeks between late July and mid-September in 2012 and 2013. About six years elapsed between the capture of the first specimen in December 2008 and recognition of H. halys as an agricultural pest in late 2014.