Response of \u3ci\u3eTribolium castaneum and Tribolium confusum \u3c/i\u3e adults to vertical black shapes and its potential to improve trap capture

Tribolium castaneum and Tribolium confusum can be monitored in food processing facilities using traps baited with pheromones and kairomones, but beetle response to traps might be enhanced by adding visual cues. Against a white background, T. castaneum adults were more likely to visit black pillars than white pillars when presented with a choice (e.g., 73% of beetles visited black and 17% visiting white pillar), and visits to black pillars increased with pillar height. When tested against a black background, beetles did not show a significant preference for either color pillar regardless of height. When comparing beetle’s captures in pheromone/kairomone baited traps placed in front of a white or black panel in a white arena under high, low, or dark light conditions, more beetles were captured in traps in front of black panels under both high and low light conditions, but not under dark conditions. A similar pattern of capture under low light and dark conditions was also found for the closely related species T. confusum. In a larger scale choice test, the same pattern of greater T. castaneum captures in traps in front of black panels than white panels was obtained, whether traps were placed in corners or along walls. Our results suggest that captures in monitoring traps could be increased by adding dark vertical shapes behind trap locations or placing traps near dark structures