POLLEN MORPHOLOGY AND ITS EFFECT ON POLLEN COLLECTION BY HONEY-BEES, APIS-MELLIFERA L (HYMENOPTERA, APIDAE), WITH SPECIAL REFERENCE TO UPLAND COTTON, GOSSYPIUM-HIRSUTUM L (MALVACEAE)

Honey bees, Apis mellifera, forage readily on flowers of upland cotton , Gossypium hirsutum, to harvest nectar. The abundant pollen gets caug ht in the haircoat of the bees, but cotton pollen is nevertheless rare ly collected. Honey bee pollen collection effectiveness was therefore investigated in a flight room using cotton and five other spheroidal p ollen taxa presented in sequence. Honey bees visited all pollen dishes , but okra pollen (Abelmoschus esculentus) was never packed successful ly by the bees landing in the pollen dish. Cotton pollen was collected by 16% of the landing foragers, pumpkin pollen (Cucurbita pepo) by 71 %, and pollen of corn (Zea mays), pigweed (Amaranthus palmeri), and su nflower (Helianthus annuus) were readily collected by nearly all forag ers. The amount of time spent in the pollen dish was always short (1 t o 9 seconds) and homogeneous among all pollen taxa, indicating that no ne of them was strongly repellent to the bees. The reduced effectivene ss with which honey bees collected cotton pollen was demonstrated by t he longer amount of time needed for pollen grooming and packing betwee n two consecutive landings in the pollen dish and the small size of co tton pollen pellets (averages of 0.42 mg and 8.23 mg per pellet for co tton and corn pollen, respectively). This reduced efficiency in cotton pollen collection was associated primarily with the length of the spi nes on cotton pollen which physically interfered with the pollen aggre gating process used by honey bees.