EFFECT OF FEMALE AGE ON DAILY CYCLE OF SEXUAL PHEROMONE EMISSION IN GREGARIOUS EGG PARASITOID ANAPHES LISTRONOTI

The temporal pattern of pheromone emission by Anaphes listronoti femal es was established in a four-arm olfactometer by observing, at 2-hr in tervals, the response of <2-hr-old males to odor produced by individua l virgin females of <1, 1, and 2 days of age. This is the first eviden ce of a sexual pheromone in a Mymaridae. Under a 16L: 8D photoperiod a nd 24 degrees C constant temperature, the responsiveness of males to f emales of different ages varied significantly during the photophase. W hen <1-day-old females were used, males made significantly more final choices in the pheromone field than odorless fields at 4 and 6 hr afte r the onset of the photophase, and their walking speed was significant ly higher from 4 to 12 hr, suggesting that females began to release a long-range pheromone during this period. Final choices and high walkin g speed were observed earlier with 1- and 2-day-old females than with <1-day-old females, and there was a significant decrease in male respo nses at 6 hr after the onset of the photophase, suggesting a bimodal t emporal pattern of sexual pheromone emission.