Abstract
The strong attractiveness of logs infested with female ambrosia beetles, Trypodendron lineatum (Oliv.), to the flying population was sharply reduced after the addition of males. The field response of T. lineatum was greatly reduced when air from logs infested with attractive females was mixed with air passing over logs infested with both sexes. The findings suggest that females keep producing the attracting principle in the presence of males. Males appear to reduce secondary attraction by producing a volatile substance(s) which may be anti-aggregating or repellent in its effect.