G. Isham et D. Eisikowitch, THE BEHAVIOR OF HONEY-BEES (APIS-MELLIFERA) VISITING AVOCADO (PERSEA-AMERICANA) FLOWERS AND THEIR CONTRIBUTION TO ITS POLLINATION, Journal of Apicultural Research, 32(3-4), 1993, pp. 175-186
Observations of honey bee (Apis mellifera) foraging behaviour on five
cultivars of avocado (Persea americana) were carried out in 1982-1984
and 1990-1992 in Galilee, Israel. Examination of the morphology of avo
cado flowers showed that the pistillate and staminate flower stages ha
ve similar structures. Bees collecting nectar, or nectar and pollen, v
isited both pistillate and staminate flowers, and due to the flower st
ructure they were forced to touch both pistil and anthers. Only limite
d sites on a bee's body contacted the anthers, and these 'collection s
ites' also contacted the stigma, which occupied the same position as t
he anthers of the inner stamens. Most avocado pollen grains on bees vi
siting staminate flowers were clumped at the 'collection sites' and co
nstituted the main pollen available for pollination. Some pollen grain
s randomly distributed over the entire bodies of bees visiting either
pistillate or staminate flowers could have been acquired inside the hi
ve, and did not play an important role in pollination. The observation
s suggest that pollination within a cultivar is accomplished during th
e overlapping phase of its pistillate and staminate flowering, during
which bees collecting nectar and pollen move freely among neighbouring
staminate and pistillate flowers. Pollination between cultivars of op
posite flowering type is carried out by bees moving between them throu
ghout the overlapping period of pistillate flowering of one cultivar a
nd staminate flowering of the other. Bees which collect only pollen us
ually do not visit pistillate flowers and do not contribute to pollina
tion.