INVASIVE PLANT-FEEDING INSECTS ARE A CONSTANT THREAT TO AGRICULTURE IN THE UNITED STATES. OF PARTICULAR CONCERN ARE WHITEFLIES AND SCALE INSECTS, MANY OF WHICH CAN CAUSE SIGNIFICANT MECHANICAL DAMAGE TO CROPS AND TRANSMIT PLANT DISEASES. DUE TO THEIR SMALL SIZE AND INCONSPICUOUS APPEARANCE, THESE INSECTS FREQUENTLY GO UNNOTICED UNTIL INFESTATIONS ARE WELL-ESTABLISHED AND WIDESPREAD DAMAGE HAS ALREADY OCCURRED. BIOLOGICAL CONTROL, THE SUPPRESSION OF PEST INSECT POPULATIONS BY THEIR NATURAL ENEMIES (INSECT PREDATORS AND PARASITES), PROVIDES COST EFFECTIVE, CONTINUOUS, AND MAINTENANCE-FREE CONTROL OF INVASIVE PEST INSECTS AND CAN KEEP INSECT POPULATIONS AT LOW ENOUGH DENSITIES TO AVOID ECONOMIC DAMAGE. THE PARASITIC WASP GENUS ENCARSIA HAS BEEN USED IN SOME OF THE MOST SUCCESSFUL BIOLOGICAL CONTROL PROGRAMS, OFTEN SAVING HUNDREDS OF MILLIONS OF DOLLARS IN PEST CONTROL COSTS. GIVEN PAST SUCCESSES, ENCARSIA SHOULD PROVE USEFUL IN FUTURE BIOLOGICAL CONTROL ENDEAVORS OF ONGOING AND EMERGENT AGRICULTURAL PEST OUTBREAKS.SUCCESSFUL BIOLOGICAL CONTROL PROGRAMS ARE RELIANT UPON A SPECIALIST'S ABILITY TO INVEST IN THE CORRECT NATURAL ENEMY FOR THE PEST THEY ARE TRYING TO CONTROL. IN UNDERSTUDIED GROUPS LIKE ENCARSIA, THE LACK OF BIOLOGICAL KNOWLEDGE CAN IMPEDE THIS PROCESS. THE GOAL OF THIS PROJECT IS TO DESCRIBE THE EVOLUTIONARY RELATIONSHIPS OF ENCARSIA. TO DO THIS WE WILL CONSTRUCT A PHYLOGENETIC TREE (A DIAGRAM OF EVOLUTIONARY RELATIONSHIPS) BASED ON DNA SEQUENCES FROM SPECIES OF ENCARSIA COLLECTED AROUND THE WORLD. WITH THIS PHYLOGENETIC TREE WE WILL BE ABLE TO (1) MAKE PREDICTIONS ABOUT THE BIOLOGY OF UNKNOWN SPECIES OF ENCARSIA, (2) PREDICT TRAITS AND BEHAVIORS OF IMPORTANCE TO SUCCESSFUL BIOLOGICAL CONTROL, (3) PROVIDE IDENTIFICATION RESOURCES INFORMED BY THE PREDICTIVE POWER OF THE PHYLOGENETIC TREE, AND (4) MODERNIZE THE TAXONOMIC CLASSIFICATION OF ENCARSIA. BY ENABLING SPECIALISTS TO MAKE BIOLOGICAL CONTROL DECISIONS IN AN EVOLUTIONARY CONTEXT, OUR RESEARCH WILL EXPEDITE THE IDENTIFICATION, EVALUATION AND SELECTION OF NATURAL ENEMIES OF POTENTIAL USE IN BIOLOGICAL CONTROL AND AVOID THE COSTLY MISTAKES THAT HAVE HISTORICALLY CAUSED DELAYED SUCCESS OR FAILURE IN BIOLOGICAL CONTROL PROGRAMS. SUCCESSFUL BIOLOGICAL CONTROL PROVIDES COST EFFECTIVE, CONTINUOUS, AND MAINTENANCE-FREE CONTROL OF INVASIVE PEST INSECTS AT A REDUCED ECONOMIC IMPACT TO FARMERS AND THE AGRICULTURAL INDUSTRY.