In their study, Harvard biologists made use of 20,000 observations made over 19 years by the Massachusetts Butterfly Club between 1992 and 2010.
Butterfly bios from Harvard's press kit:
The giant swallowtail (Papilio cresphontes), a southern butterfly historically only seen as an occasional stray in New England, has been present in conspicuously high numbers in Massachusetts in recent years, with scores of reports in 2011 and 2012. This individual (at top) was photographed August 15, 2012 in Westport, Ma. (Photo credit: Frank S. Model).
Observations of the zabulon skipper (Poanes zabulon), another southern butterfly historically rare in Massachusetts, have increased by 18 fold in the past 19 years. This individual (at left) was photographed August 15, 2012 in Westport, Ma. (Photo credit: Frank S. Model).
The Atlantis fritillary (Speyeria atlantis) (above left) and Acadian hairstreak (Satyrium acadica) (above right), both northerly distributed species, have declined by more than 80% in Massachusetts in the past 19 years but have no formal protection, while the southerly distributed frosted elfin (Allophrys irus) (below), which has increased by 1000% in the same period, receives formal protection and active management in Massachusetts (Photo credits: Frank S. Model).