PHEROMONE PRODUCTION BY MALE ANASTREPHA-SUSPENSA (DIPTERA, TEPHRITIDAE) UNDER NATURAL LIGHT CYCLES IN GREENHOUSE STUDIES

Collections of volatiles were obtained from calling males of the Carib bean fruit fly, Anastrepha suspensa (Loew), under natural light cycles in tests conducted in a greenhouse and compared with collections from males tested under standard laboratory conditions. There was no effec t on total amount of pheromone or in amounts of individual components released between 0400 and 2100 hours (EST); i.e., from 2 h before unti l 2 h after a 12-h photophase. Pheromone periodicity under either regi me was fit best by a bimodal distribution, but there were shifts in ti mes of peak production. Under laboratory conditions, there was a small early morning peak at the start of photophase (0600 hours) and a broa d afternoon peak almost-equal-to 4 h before the end of photophase. Und er greenhouse conditions, there was a small, broad early morning peak at 0700 hours and a sharp afternoon peak at almost-equal-to 1700 hours . Flies in the laboratory released significantly higher amounts of vol atiles from 1230 to 1630 hours, whereas those in the greenhouse produc ed significantly higher levels from 1700 to 2100 hours. Under greenhou se conditions, pheromone production was positively correlated with rel ative humidity and negatively correlated with light intensity, as indi cated by overall light levels measured in lux. It is speculated that h igh light intensities and low relative humidity, to which males under natural light cycles are exposed, inhibit pheromone production during the middle part of the day, and that environmental variables work in c oncert with circadian rhythm to control periodicity of pheromone relea se.