Biology and larval morphology of Ceutorhynchus neglectus (Coleoptera: Curculionidae), a minor pest of canola (Brassicaceae) in western Canada.

摘要

The life history, behaviour, and host plant feeding preferences of Ceutorhynchus neglectus were studied on rape (Brassica napus and B. rapa) in Alberta and Saskatchewan during 1995-97. The final-instar larva is described for the first time. C. 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). Mate-guarding behaviour was observedfor males, which remained attached to females after copulation was completed and 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, andconstructed 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 as feeding sites. In contrast to Phyllotreta cruciferae, which fed indiscriminately over the entire cotyledon surfaces of rape seedlings, adults of C. neglectus caused less cotyledon damage per individual and tended to feed on cotyledon edges. It is concluded that C. neglectus should remain a minor pest of rape, and can only be expected to invade the crop when its preferred host (flixweed) is unavailable.