Natural history of Reduvius personatus Linnaeus (Hemiptera: Heteroptera: Reduviidae) in North AmericaAbstract : Reduvius personatus is commonly known as the masked bed bug hunter. It is a European species which has successfully adapted to life in North America, where it was introduced at an unknown date. My study of the biology, ecology and distribution of this insect is from 1997-2012 in southern Quebec and Ontario, Canada. Adults were found in spring and summer, both inside and outside dwellings. Third and fifth nymphs were present indoor during the winter as well. Third and fifth nymphal instars exhibited dormancy during the first and second winter, respectively. Nymphs exude a sticky substance which facilitates body-masking with dust particles. This camouflage has given rise to the alternative names “masked bug” or “masked bed bug hunter”. Mating occurs in a lateral orientation. Four successive generations reared over a decade showed a two-year life cycle. The adult morphology, first instar, characteristics of egg, embryonic development, feeding, mating, and cannibalistic behaviour were studied and are illustrated. The distribution in its adapted (North America) and native (Western Palaearctic) habitats was studied and mapped. This insect was not found to be harmful to humans and household pets. This is the first long-term natural history study of R. personatus, in North America.