Ptilothrix bombiformis (Hymenoptera: Apoidea) is a specialist bee belonging to the tribe Emphorini. The emphorine phylogeny suggests that Convolvulacea is the ancestral plant family and independent evolutionary host-switches to several unrelated plant families have occurred. The role of floral scent has been well-characterized in pollination systems involving moths, butterflies, bumblebees, and honeybees, but little is known about how specialist bees mediate host selection, or how host-choice evolved in specialist bees. This research investigates the role of floral scent in host selection by P. bombiformis. Ptilothrix bombiformis has traditionally been classified as a Hibiscus (Malvaceae) oligolege. My research shows that it can now be placed into a more detailed dietary classification as an eclectic oligolege because it also collects pure pollen loads from a distantly-related plant, Ipomoea pandurata (Convolvulaceae). Using dynamic headspace sampling and gas chromatography-mass spectrometry, I obtained floral chemical profiles for Hibiscus moscheutos ssp. lasiocarpos and Ipomoea pandurata. Both flowers contain aliphatics, aromatic compounds, monoterpenes, and sesquiterpenes. The host flowers have 14 shared compounds in their floral scent, which may be responsible for the bees' ability to recognize and utilize I. pandurata, a member or the emphorine ancestral host-plant family. Some of these shared compounds are also found in other emphorine host plants and may be responsible for their constraint in host-use.