efficiency of pollination by ensuring that compatible pollen is transferred among conspecific flowers when needed.

Perhaps of greatest significance to the economic importance of A. mellifera is that apiculture—the management of honey bees—is a highly developed discipline that has made bees and beekeeping equipment widely available. Honey bees have been used in North Amercia to provide pollination services for crops in bloom in extensive areas. Typically, one-quarter to one-third of workers in a colony during flight season are foragers. Honey bees can be concentrated in very high densities, which are required for effective pollination in large monocultures with extremely high floral densities, and they can be transported by truck to any location at any time crops are in bloom. Finally, because honey bees can be cared for and maintained by humans, they are buffered to some extent from declines in environmental quality.

Honey bee populations have followed different trends in the three North American nations. In the United States, data from the USDA National Agricultural Statistics Service (NASS) reveal declines in the number of honey bee colonies producing honey during 1947–1972 and 1989–1996 (Figure 2-1) (USDA-NASS, 1995, 1999, 2004a, 2005, 2006a). Overall, the number of managed colonies dropped from 5.9 million in 1947 to 2.6 million in 1996–2004. That number fell again in 2005 to 2.4 million. The decline from 1985 to 1996 is likely linked to the occurence of the tracheal mite,

FIGURE 2-1 U.S. honey bee colonies, 1945–2005. Data compiled from USDA-NASS (1995, 1999, 2004a, 2005, 2006a).

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