Aging and development in social insects with emphasis on the honey bee, Apis mellifera L.

Honey bee co 'lonies typically consist of about 20-40 thousand workers, zer o to few thousand males (drones), depending on the time of year, and a sing le queen, the mother of the colony. Workers typically live 3-6 weeks during the spring and summer and can live about 4 months during the winter. Queen s are longer lived. Anecdotes of queens living 2-3 years are not unusual, t hough they normally live less than a year in commercial hives. Little is kn own about the life span of drones. Queens develop from fertilized eggs that are not different from the eggs th at develop into workers. Queens are, however, twice as large, have speciali zed anatomy, live much longer, and develop faster from egg to adult. All of these differences are derived from differences in larval rearing environme nt, primarily nutrition. The developmental trajectory of a female larva fro m worker into a queen can be determined as late as the third day of larval development, after this time the developmental pathway is fixed for a worke r phenotype. The total time of larval development is only 5-6 days, therefo re, just 2-3 days of differential feeding can lead to profound differences in development, and longevity. Workers undergo age development after they become adults. Workers usually i nitiate foraging behavior when they are 2-3 weeks old. The age at which a w orker initiates foraging is a strong determinant of her length of life. Thi s is presumed to be a result of the hazards of foraging, but natural senesc ence also occurs. Some bees remain in the nest and are never observed to fo rage, thereby outliving their forager sisters. Corresponding to this behavi oral development are changes in the sizes of glands and the production of g landular products, increases in biogenic amine titers within the brain, an increase in the volume of specific regions of the brain, and changes in the neural system that affect perception of stimuli, and learning and memory. These age-related changes in behavior are regulated by intrinsic and extrin sic factors. Genetic variation has been demonstrated for many of these life history and behavioral traits. Selection and genome mapping studies have d emonstrated relationships between the neural system, behavior, and life his tory traits. (C) 2001 Elsevier Science Inc. All rights reserved.