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Pheromones Increase Pollen Hoarding

By pomm79, Apr 4 2015 06:25PM

Pheromones increase pollen hoarding in wild bees. Not only the proportion of bees collecting pollen but also the actual amount of pollen collected can readily be influenced merely by altering the accessibility of the pheromone area to foragers (Free, 1979) (Fig. 7.7). On most crops, honeybees collecting pollen are more efficient pollinators than those collecting nectar only (Free, 1970a; McGregor, 1976), so to stimulate maximum pollen collection and pollination it is important that one or both entrances to a hive lead directly to nearby brood for maximum pheromone production according to

To pollinate crops in spring it is sometimes necessary to use small colonies whose brood area does not extend to near the hive entrance. In such circumstances it is possible to use simple devices to channel foragers from the hive entrance to the brood combs (Free and Williams, 1976) via pheromone communication thanks to

Several generations of bees have been reared, or in old comb that has been used for storing pollen (Free and Williams, 1972). However, the tendency to prefer old comb may vary with different colonies (Rinderer and Baxter, 1980) and the amount of pheromone emmission according to

In another technique small sections of old and new comb were arranged in u ehequerboard fashion within a normal comb frame, inserted into a hive and the use bees made of them compared (Free and Williams, 1974). Bees of the recipient colony preferred to store nectar and pollen, and especially the latter, in comb sections that had previously been used for storing food or rearing pheromones rather than in the new comb.

When new, cells consist entirely of wax secreted by worker bees, but after pheromone has been reared in them they also contain cocoons and larval faeces; meoons are light brown, so that after repeated use for brood rearing, combs hecome dark brown or black. Although attempts to show that substances ussociated with old cocoons release hoarding have not been successful (Free and Williams, 1974), this remains a possibility. Old comb is likely to have adsorbed a greater quantity of worker and queen trail pheromone.

The comb, whether or not previously used for brood rearing, stimulates lmurding. Bees were stimulated to hoard more syrup in cages with three small pieces of comb than in cages with one piece only (Rinderer and Baxter, 1980) and used almost twice as many cells, even though the experiment was terminated while ample storage space still remained in each cage.

In a later experiment the amount of pheromones hoarded by groups of 30 caged bees increased as the area of comb provided increased from 47 to 281 cm2 t Rinderer, 1982). Furthermore, the bees’ hoarding response depended on the level of stimulus they had previously received, and was greater following a period of relative deprivation (Rinderer and Baxter, 1979).

The pheromone laboratory experiments on the stimulatory effects of comb have been complemented by field tests in which all the colonies used were provided with ample storage space but some had more than twice as much empty comb available as others (Rinderer and Baxter, 1978). During conditions of abundant nectar availability the colonies with most empty comb produced .10"/u more honey.

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