BIOASSAY SYSTEM FOR COLLECTING VOLATILES WHILE SIMULTANEOUSLY ATTRACTING TEPHRITID FRUIT-FLIES

A bioassay system was developed that permits the testing of various su bstrates for biological activity in a flight tunnel, while simultaneou sly collecting a portion of the volatiles from the attractive source f or subsequent chemical identification and quantification. Bioassays of the response of virgin female Caribbean fruit flies, Anastrepha suspe nsa (Loew) (Diptera: Tephritidae), to volatiles released by calling ma les were conducted in a greenhouse under natural light cycles and fluc tuating environmental conditions, similar to those in the field. Using this system, the periodicity of response of the female flies between 1300 and 1945 hr (EST) was tested. Fifty to 75% response occurred betw een 1700 and 1845 hr. Mare pheromone release was greatest between 1500 and 1800 hr. Videotaped records of insects, taken between 1700 and 18 00 hr as flies approached and entered the traps, were analyzed to inte rpret the communicative role of the volatiles released. Significantly more flies landed on and entered the pheromone-emitting trap than the control trap. There was no difference in the amount of time spent on t he trap face, an indication that volatiles were attractants. The syste m described should be of general utility in determination of the attra ction of pest fruit flies to suspected attractants.