The Pterourus glaucus complex in three southern New England states is analyzed for cryptic speciation. What was historically considered to be one species, P. glaucus (Linnaeus, 1758), was recently split to separate P. canadensis (Rothschild & Jordan, 1906) at species rank (Hagen et al., 1991). Additionally, P. appalachiensis Pavulaan & Wright, 2002, was described as an Appalachian Mountain endemic. The western member of the complex, P. rutulus (Lucas, 1852), has frequently been considered a subspecies of P. glaucus (Scott, 1986; Tyler, Brown & Wilson, 1994), as was P. alexiares (Höpffer, 1866) (Tyler, Brown & Wilson, 1994). Recently, a bimodal emergence pattern was identified in populations across a regional band stretching from southern New England, through central New York (Hagen & Lederhouse, 1985), northeastern Pennsylvania (Monroe & Wright, 2017) and into southern Ontario (Schmidt, 2020). This bimodal pattern encompasses two univoltine taxa: an earlier, spring-flying taxon with slightly closer morphological affinity to canadensis; and a later, summer-flying taxon with a closer affinity to glaucus. The early-flight taxon is here described as a new species, most likely of hybrid origin similar to appalachiensis. The late-flight taxon, tentatively referred to as the “Mid-Summer Tiger Swallowtail” (Wang, 2017; Schmidt, 2020), also likely of hybrid origin, appears to be undergoing rampant hybridization with glaucus in southern New England, though there is evidence it has achieved early stages of speciation in Ontario.