FLIGHT INITIATION AND FLIGHT ACTIVITY IN PROSTEPHANUS-TRUNCATUS (COLEOPTERA, BOSTRICHIDAE)

In an outdoor experimental set-up, the number of Prostephanus truncatu s (Horn) flying from maize cobs was recorded over 38 observation weeks . Flight activity in the field was recorded for 50 weeks with three ph eromone traps, each placed at c. 100-300 m from the first experimental set-up. Multiple regression analyses revealed that both flight initia tion and flight activity were partly influenced by mean temperatures, but were not directly related. Flight initiation was mainly dependent on population density. An additional experiment showed that sex ratios among pheromone trap catches were not correlated with the number of b eetles caught; sex ratios were female-biased throughout the year. Seas onal fluctuations in flight activity recorded with pheromone traps are mainly dependent on changes in the number and sizes of beetle populat ions in a given area, as well as on breeding site availability and sui tability.