2226Most of the insect pollinators of Brassica crops belong to Apis species. Foraging rate is one of the important factors to compare pollination efficiency of different bee species. In general, more the foraging frequency, more the chances of pollination. The number of flowers visited per minute by any bee species depends upon the number of factors including instinctive foraging behaviour, length of proboscis (Inouye, 1980) floral structure (Free, 1970) particularly the corolla depth (Gilbert, 1980) type and quantity of floral rewards (Rao & Suryanarayana, 1990; Rao, 1991) density of flowers on particular cultivar of the crop concerned and hours of the day. The present paper reports the comparision of foraging rates of various honeybee species on parental lines of B. napus at different hours of the day.Experimental plots (10.5 x 1.5meter) were raised for hybrid seed production under Punjab conditions by using seeds of cytoplasmically male-sterile (CMS) line (TCMS-PR-05) and restorer (R) line (TFR-91) of B. napus hybrid PGSH-51, during year 1998-99, by following recommendations of Punjab Agricultural University, Ludhiana (Punjab). Selected ratio of male to female rows were 2:4. R line plants showed inflorescence about 15 days earlier than those of CMS line. In order to make the flowering synchronous in both the parental lines, early flowering plants were detopped. Foraging activity of A. dorsata was enough in the area selected for study because two colonies of this bee species were present in nearby area. Two hives of A. florea were procured from other places and transplanted at suitable places (piles of dried sticks arranged just like natural habitat) in the field. In order to compare foraging rates of four honeybee species, two colonies each of A. mellifera and A. cerana were managed. Number of flowers visited per minute by a particular bee was counted with the help of a stop watch.
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