How- ever, the extraction time still did not meet the practical purpose (fast method) so it was further adjusted to a shorter time of maximum 2 h. Within 2 h, detection of volatile pheromone released from six beetles could not be achieved, so more insects were added until the volatile pheromone was detected. The final population was thirteen male beetles in 1 kg of flour and the amount of volatile pheromone released was found to be approximately 0.43 mg (n 1⁄4 3).
Ferlc I and II were detected when there was a total of twenty four beetles at 30 C for 4 h and they produced approximately 1.22 and 1.35 mg for Ferlc I and Ferlc II respectively (n 1⁄4 3). The extrac- tion time was not further adjusted because volatile pheromone may not be detected in a shorter time and hence addition of more beetles was not considered as meaningful. Such large insect pop- ulation could easily be detected by visual inspection.
A population of 50 beetles were the minimum number of C. pusillus that were needed for detection at 30 C for 4 h and compound I released was about 0.22 mg (n 1⁄4 3). Like C. ferrugineus, the extraction time was not further adjusted as adding more beetles was not meaningful, as stated above.