Kenk R 1972 (citation)- p 44, "Northeastern parts of the U.S. north of the Delaware River and eastern Canada as far west as Ontario."
Kenk R 1970 (citation)- p 13, 'Little is known about the ecological requirements of P. woodworthi. It is generally taken in ponds and rivers, more rarely in cold streams and springs. The fact that it often shares its habitat with such eurythermic species as Dugesia tigrina (Girard) and Procotyla fluviatilis Leidy suggests that it tolerates greater temperature fluctuations that does P. gracilis.'
Ball & Reynoldson 1981 (citation)- p. 88, "The introduction of thos species has probably occurred from cocoons on equipment brought over by American scientists in search of the Loch Ness 'Monster'. It is a large and vigorous species and its spread in Britain should be monitored."
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