The flight of the ambrosia beetles, Trypodendron lineatum (Oliv.), Gnathotrichus sulcatus Lec. and G. retusus Lec., revealed distinct diurnal and seasonal patterns that were influenced by environmental factors, particularly temperature, wind, and daylight. While Trypodendron flies during the entire day when the temperature is favorable, the Gnathotrichus species exhibit a peak of flight at dusk. The temperature thresholds of emergence and initiation of flight for Trypodendron and the threshold for flight of Gnathotrichus were established.
The substance responsible for mass attraction of Trypodendron, after the initial invasion of a few pioneer beetles, was found to be a species-specific sex pheromone produced by sexually mature females after entering the host. The pheromone has been concentrated from the female borings in the laboratory, and when released in the field it caused the beetles to respond. Both species of Gnathotrichus, on the other hand, responded to the borings produced by female beetles of Dendroctonus pseudotsugae Hopkins and to the extract prepared in alcohol. This fact suggests possible use of these substances in control of these ambrosia beetles.