THE USE OF ANTIBIOTICS TO TREAT PATHOGENS IN U.S. FRUIT TREE ORCHARDS HAS GROWN EXPONENTIALLY IN THE LAST DECADE, YET LITTLE IS KNOWN ABOUT ITS EFFECTS ON NON-TARGET ORGANISMS. THIS IS CONCERNING BECAUSE SHORT-TERM EXPOSURE TO ANTIBIOTICS CAN CHANGE THE MICROBIOME--COMMUNITIES OF SYMBIOTIC BACTERIA LIVING WITHIN ANIMALS--OF BENEFICIAL INSECTS, WHICH ARE KNOWN TO MODULATE BEHAVIORS ASSOCIATED WITH INSECT FORAGING. SUCCESSFUL FORAGING IS KEY TO INSECT FITNESS AS WELL AS CROP POLLINATION. MOREOVER, LONG-TERM EXPOSURE TO LOW CONCENTRATIONS OF ANTIBIOTICS MAY DRIVE THE DEVELOPMENT OF ANTIBIOTIC-RESISTANT MICROBIOMES. THIS PROJECT FOCUSES ON THE IMPACT OF CROP ANTIBIOTIC APPLICATIONS ON THE MICROBIOMES AND FORAGING BEHAVIOR OF BEES. FORAGING AND MICROBIOME DATA FROM FIELD EXPERIMENTS IN PEAR(PYRUS COMMUNIS) ORCHARDS--A CROP HIGHLY DEPENDENT ON POLLINATORS FOR FRUIT SET AND THAT REQUIRES ANTIBACTERIAL SPRAYS AT BLOOM--WILL BE PAIRED WITH LABORATORY ASSAYS, FOCUSED ON LINKING BEE GUT MICROBIOMES TO FORAGING BEHAVIOR. SPECIFICALLY, WE WILL 1) QUANTIFY TRACES OF ANTIBIOTICSIN FLOWERS AND EASTERN BUMBLE BEE (BOMBUS IMPATIENS)COLONIES PLACED IN PEAR ORCHARDS AND ASSESS THE IMPACT ON A) COLONY-LEVEL GUT MICROBIOME COMPOSITION (ABUNDANCE OF CORE BACTERIA TAXA AND ANTIBIOTIC-RESISTANT GENES) AND B) INDIVIDUAL AND COLONY-LEVEL FORAGING; 2) TEST IF GUT MICROBIOME CHANGES ALONE CAN DRIVE INDIVIDUAL CHANGES IN BUMBLE BEE LEARNING, MEMORY, AND FORAGING IN THE LAB. THIS WORK WILL FURTHER OUR UNDERSTANDING OF THE IMPACT OF FIELD ANTIBIOTIC EXPOSURE ON AGRICULTURALLY IMPORTANT INSECTS AND ON THE ROLE OF THE MICROBIOME IN MODULATING POLLINATOR HEALTH.