Abstract: The efficacy of a flour beetles trap, baited with 1mg of racemic 4,8-dimethyldecanal,was evaluated. The trap had the shape of a truncated pyramid with a squared basis and a roundedcentral pitfall with perpendicular walls. Externally the trap was made of flocked PVC, while thetop and the pitfall were made of smooth PVC in order to prevent the escape of caught beetles.Tests were carried out in a squared room (area 34m2; volume 103m3) with constant conditions of26±1°C, 70±5% RH. The conditioning unit was placed at a height of 1.56m, and separated by0.85m from the corner of the wall; the opening of the air flow was 0.97×0.29m. Tests werecarried out by rotating the traps placed in different positions (10cm from the wall): a) one traprotated among the different corners, b) two traps rotated together in the different corners, and c)five traps, of which one was put into the centre of the room and four in the different corners. Anequal number of adults of Tribolium castaneum and T. confusum were introduced in the room. Inthe tests a) and b), 240 adults were released in the room. Test c) was carried out on groups of 80,160 or 240 adults. Three replicates were carried out for each test. In all the tests, the number ofadults of T. confusum caught by the traps was greater than the one of T. castaneum. The highestnumber was always observed in a trap located at a particular position, regardless of the number oftraps present in the room. In test c) the percentage of adults decreased while the number ofreleased individuals increased.