The extraction 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.