The Canadian Entomologist
Franklin (1913) ( p. 448) stated, "There is not yet a single new world account of a Psithyrus having been found in a Bombus nest". Since then, of the seven North American species, four have been reported found in nests of Bombus spp. by Sladen (1915), Frison (1916, 1921, 1926), Plath (1934), Linsley (1944), and Leech (194 7). Of these records only two are from Canada, both being from British Columbia. Siaden (1915) reported finding the well-preserved body of a female of Psithyrus insularis (Sm.) and several cocoons, from one of which he extracted a male of P . insularis, in a nest containing an old queen and several workers of Bombus flavifrons Cress. Leech (1947) found a P. insularis female in a nest containing several workers of Bombus mixtus Cress., and concluded that the iniquiline had supplanted the mixtus queen.
Craig, C. H., "Psithyrus insularis (Sm.) in a nest of Bombus ternarius Say (Hymenoptera: Bombidae)" (1953). Co. Paper 153.
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