500ml container has holes on both top and bottom ends. The top end hole is for the spreading of the bait odour to the environs while the bottom hole is to capture the attracted insects. Once the attracted insects near the bait trap they try to feed on to the bait. For example ripened fruit. While trying to feed on to the food the insect find a way into the trap through the bottom hole where the opening is edged inside into the trap while makes extremely unlike for a flying insect to come out of the trap which as a protruded hole in side into the trap