Technical Abstract: Males of the fruit fly parasitoid D. longicaudata are found in aggregations that give the appearance of leks. Males perform bouts of wing fanning both when alone and in the presence of other conspecifics. The acoustic signals produced by this wing fanning have been documented (Sivinski & Webb 1989, Annals ESA 82: 116-120). In other insects, wing fanning may be also used to disperse pheromone from the male or to increase airflow over the male, improving male orientation to female odors (Vinson 1972, Env. Ent. 1: 409-414). Among Hymenoptera that use them, female-produced pheromones tend to be released in small quantities and are used for short-range attraction, while male-produced pheromones are released in larger quantities and are used for long-range attraction. It is not known if D. longicaudata use either or both. Therefore, laboratory studies were conducted to determine if pheromones are used for communication by D. longicaudata. Video analysis of male-female interactions, and olfactometer and flight tunnel studies were used to evaluate response of virgin parasitoids to opposite sex individuals. Results of these studies indicate that males release a long-range pheromone that is used by females to locate calling males, and that females release a pheromone that is used for short-range communication with males. Chemical analysis is underway to identify, quantify and formulate components released by calling males. Availability of a synthetic pheromone-based trapping system for this parasitoid would add a valuable tool to document its successful use in biological control.