A study was undertaken to determine aspects of the life history, behaviour, and host plant feeding preferences of Ceutorhynchus neglectus Blatchley, a minor pest of canola, Brassica napus L. and Brassica rapa L., in western Canada. The final-instar larva was described for the first time. Ceutorhynchus neglectus was univoltine, with adults first occurring on host plants in early June. Mating occurred throughout June and July, and eggs were laid into the distal ends of developing siliques of flixweed, Descurainia sophia (L.) Webb (Brassicaceae). Mate guarding behaviour was observed for males of C. neglectus, which remained attached to females long after copulation was completed and, if necessary, struggled with rival males to prevent them from fertilizing their mates. Larvae fed upon developing seeds and, when mature, bored through the pods, dropped to the soil, and constructed earthen cells approximately 2 cm beneath the soil surface where they pupated. Results from laboratory host preference studies were consistent with field observations which indicated that among selected species of Brassicaceae, leaves and siliques of D. sophia were preferred by adults of C. neglectus as feeding sites. In contrast to flea beetles, Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae), which fed indiscriminantly over the entire cotyledon surfaces of canola seedlings, adults of C. neglectus caused less cotyledon damage per individual and tended to feed on cotyledon edges. Because of its biology and host plant preferences, C. neglectus should remain a minor pest of canola, and can only be expected to invade the crop when its preferred host (flixweed) is unavailable.