Task-related differences in the cuticular hydrocarbon composition of harvester ants, Pogonomyrmex barbatus

Colonies of the harvester ant, Pogonomyrmex barbatus, perform a variety of tasks. The behavior of an individual worker appears to depend on its recent history of brief contacts with ants of the same and other task groups. The purpose of this study was to determine whether task groups differ in cutic ular hydrocarbon composition. We compared the cuticular hydrocarbon composi tion of ants collected under natural conditions as they performed one of th ree tasks: patrolling (locating food sources), foraging, or nest maintenanc e. Task groups differed significantly in the relative proportions of classe s of hydrocarbon compounds, as well as in individual compounds. Relative to nest maintenance workers, foragers and patrollers had a higher proportion of straight-chain alkanes relative to monomethylalkanes, dimethylalkanes, a nd alkenes. There was no significant difference in the chain length of n-al kanes among the task groups. Foragers did not differ in hydrocarbon composi tion from patrollers. Colonies differed significantly from one another in h ydrocarbon composition, but task groups differed in consistent ways from co lony to colony, suggesting that the mechanism responsible for task-related hydrocarbon composition was the same in all colonies. P. barbatus workers s witch tasks during their lifetimes, suggesting that cuticular hydrocarbon c omposition changes during adulthood as well. Nest maintenance workers are p robably younger than foragers and patrollers and perform very little of the ir work outside of the nest. Task-related hydrocarbon differences detected here may be associated with worker age, and/or the abiotic characteristics (temperature, humidity, and ultraviolet light) of the interior and exterior work environments.