**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** THIS PROJECT SEEKS TO ADDRESS TWO PROBLEMS RELATED TO THE DECLINE OF POLLINATORS, WHICH PROVIDE AGRICULTURAL SERVICES WORTH BILLIONS OF DOLLARS. FIRST, COMPOUNDING EFFECTS OF PARASITES,PESTICIDES, AND THE LOSS OF FLORAL RESOURCES ALL CONTRIBUTE TO THE DECLINE OF BENEFICIAL POLLINATORS, BUT IT ISN'T FULLY UNDERSTOOD HOW FLORAL RESOURCES,AND EFFORTS TO SUPPLEMENT THEM,WILL AFFECT THE PARASITES OF POLLINATORS, AND HOW THIS MAY DIFFER BETWEEN AGRICULTURAL AND NON AGRICULTURAL LAND. THIS PROJECT WILL STUDY HOW THESE FACTORSINTERACT IN AGRICULTURAL AND NON-AGRICULTURAL LANDSCAPES BY FOCUSING ON BUMBLE BEES, AND THE CONOPID FLIES WHICH PARASITIZE THEM.DECLINES IN BUMBLE BEES HAVE BEEN ATTRIBUTED TO NEGATIVE AFFECTS OF PESTICIDES ON REPRODUCTION, CHANGES IN CLIMATE AND LAND USE,THE PREVALENCE OF PATHOGENS, AND PARASITES. AN ADDITIONAL IMPORTANT FACTOR FOR BUMBLE BEES IS PARASITISM BY FLIES IN THE FAMILY CONOPIDAE. CERTAIN CONOPID FLIES PARASITIZE BUMBLE BEES AT RATES APPROACHING 50% DEPENDING ON THE SPECIES AND POPULATION. THESE BEES DIE 10-12 DAYS AFTER BEING PARASITIZED, WHEN THE FLY PUPATES.THREE OF THE FACTORS THAT LIKELY INFLUENCE THIS PARTICULAR HOST-PARASITE DYNAMIC ARE HOST PREVALENCE (BUMBLE BEE POPULATION), FLORAL RESOURCES,AND SOIL PESTICIDE EXPOSURE, WITH THE FOLLOWING LOGIC. CONOPID PARASITE POPULATIONS ARE INTRINSICALLY LINKED TO THEIR BUMBLE BEE HOSTS, WHICH IN THIS CASE DEPEND EXCLUSIVELY ON FLORAL RESOURCES FOR FOOD. HOWEVER, FLY POPULATIONS COULD BE REDUCED IN AGRICULTURAL LANDSCAPES BECAUSE THEY ENCOUNTER PESTICIDES IN THE SOIL WHERE THEY PUPATE, A MECHANISM WHICH IS INTENTIONALLY EXPLOITED IN THE CONTROL OF FLIES THAT PESTS OF FRUIT AND VEGETABLE CROPS. AGRICULTURAL LANDSCAPES CAN VARY GREATLY FROM WILD AREAS IN EACH OF THESE FACTORS, WHICH COULD EXPLAIN OBSERVED RATES OF PARASITISM. UNDERSTANDING HOW RATES OF PARASITISM DIFFER BETWEEN LANDSCAPE TYPES AND SPECIES WILL IDENTIFY WHETHER HABITAT ENHANCEMENTS WOULD HELP AMELIORATE THE NEGATIVE EFFECTS OF PARASITISM WHILE CLARIFYING THE IMPACT OF CONOPID PARASITISM ON BUMBLE BEE DECLINES.THIS PROPOSAL WILL DIRECTLY ADDRESS THESE GAPS BY EXAMINING PARASITISM RATES IN AN ECONOMICALLY AND ECOLOGICALLY IMPORTANT POLLINATOR IN AGRICULTURAL AND NON-AGRICULTURAL SETTINGS, AND IDENTIFYING MECHANISMS OF THE PARASITE-INDUCED BEHAVIORAL MANIPULATION BETWEEN CONOPID FLIES AND BUMBLE BEES.THIS DIRECTLY RELATES TO PRIORITY AREA 1C OF PROGRAM AREA PLANT HEALTH AND PROTECTION OF PLANT PRODUCTS:PESTS AND BENEFICIAL SPECIES IN AGRICULTURAL PRODUCTION SYSTEMS.THE SECOND PROBLEM RELATED TO THE DECLINE OF POLLINATORS HAS TO DO WITH A MAJOR BOTTLENECK IN THE BUMBLE BEE LIFECYCLE -DIAPAUSE. DIAPAUSE ISA STAGE WHERE A MATED QUEEN LASTS THE WINTER UNDERGROUND. QUEENS OF DIFFERENT BUMBLE BEESPECIES OF ENTER INTO DIAPAUSE AT DIFFERENT TIMES OF THE YEAR, BUT ALL OF THEM GO THROUGH A BEHAVIORAL SWITCH WHERE THEY SEEK SHELTER BYDIGGING INTO THE GROUND. REMARKABLY, THE CONOPIDFLY PARASITE INDUCES EVEN WORKERS BUMBLE,BEES (WHICH DO NOT NORMALLY DIG) TO DIG INTO THE GROUND BEFORE THEY DIE, ALLOWING THE FLY PUPATE IN A PLACE WHERE THEY ARE LESS LIKELY TO BE EATEN OR TO DRY OUT. HOW THE FLY MANIPULATES THE BEEIS TOTALLY UNKNOWN, BUT IS LIKELY DUE TO A SIMILAR MECHANISM THAT TRIGGERS PRE-DIAPAUSE BEHAVIOR IN QUEENS. THIS COULD OFFER A WINDOW INTO WHAT FACTORS GOVERN THE BEHAVIORAL SWITCH TODIGGING BEHAVIOR IN QUEEN BEES, ANDIS IMPORTANT BECAUSE THE TIMING OF DIAPAUSE HAS A BIG IMPACT ON SURVIVAL.THIS PROJECT WILL USE A COMBINATION OF INSECT AND FLORAL SURVEYS, MEASUREMENTS OF SOIL PESTICIDE RESIDUES, AND SPECIES IDENTIFICATION TO DETERMINE RATES OF CONOPID PARASITISM OF BUMBLE BEES IN WILD VS AGRICULTURAL LANDSCAPES.IN ADDITION, BEHAVIORAL OBSERVATIONS ANDBRAIN PROTEOMIC ANALYSES OF PARASITIZED AND NON-PARASITIZED BEES WILL BE USED TO EXAMINE MECHANISMS OF PARASITIC MANIPULATION OF DIGGING BEHAVIOR IN BEES. ULTIMATELY, THE PROJECT SEEKS TO CONSERVE BENEFICIAL POLLINATORS IN AGRICULTURAL SETTINGS.