The tobacco beetle (Lasioderma serricorne) is usually monitored by pheromone trap. Their infestation in a factory and a warehouse can be indirectly understood through monitoring data. It is impossible to directly obtain the number of tobacco beetles (population density) and seasonal prevalence of occurrence in a site. We are able to presume on-site population density from monitoring data, i.e. the number of catches. We therefore conducted a series of experiments in a warehouse to investigate relationships between the number of beetles released and the number of catches and to confirm whether fluctuation of the number of catches by pheromone trap coincided with fluctuation of population density.

Twelve NEW SERRICO traps, pheromone traps for the tobacco beetle, were attached to walls and wood boards in place of a pillar in a warehouse (roughly 24 × 36 m). The traps were put at about 10 m intervals and 1.5 m height. Fifty, 100, 200, 300 or 400 male beetles were released into the warehouse every week. Only a sex pheromone lure was used. The catches were counted a week after release. The traps were replaced by new ones every four weeks. Experiments were carried out from July to October in 2013, 2014 and 2015. Average temperature was from 20 to 34 °C and average relative humidity was from 50 to 75 %.

The two trends, the number of catches by pheromone trap and the number of individuals released, almost completely concurred in all three years. The relationship showed a highly significant positive correlation. The result suggested that fluctuation of the number of catches coincided with fluctuation of on-site population density. Moreover, because a constant capturing efficacy was obtained from experiments in the warehouse, it suggested the possibility of estimation of on-site population density based on the number of catches.