Flying Honey Bees Have among the Highest Mass-Specific Metabolic Rates Ever Measured, Suggesting that their Flight Muscles May Experience High Levels of Oxidative Stress during Normal Daily Activities. We Measured Parameters of Oxidative Stress and Antioxidant Capacity in Highly Metabolic Flight Muscle and Less Active Head Tissue in Cohorts of Age-Matched Nurse Bees, Which Rarely Fly, and Foragers, Which Fly Several Hours Per a Day. Naturally Occurring Foraging Flight Elicited an Increase in Flight Muscle Hsp70 Content in Both Young and Old Foragers; However Catalase and Total Antioxidant Capacity Increased Only in Young Flight Muscle. Surprisingly, Young Nurse Bees Also Showed a Modest Daily Increase in Hsp70, Catalase Levels and Antioxidant Capacity, and These Effects Were Likely Due to Collecting the Young Nurses Soon after Orientation Flights. There Were No Differences in Flight Muscle Carbonyl Content over the Course of Daily Activity and Few Differences in Hsp70, Catalase, Total Antioxidant Capacity and Protein Carbonyl Levels in Head Tissue Regardless of Age or Activity. in Summary, Honey Bee Flight Likely Produces High Levels of Reactive Oxygen Species in Flight Muscle that, When Coupled with Age-Related Decreases in Antioxidant Activity May Be Responsible for Behavioral Senescence and Reduced Longevity. © 2008 Elsevier Inc. All Rights Reserved.