Characterization of necromones emitted by dead Tribolium castaneum (Coleoptera: Tenebrionidae) at different densities and times in traps and their influence on attraction and recapture by conspecifics

Tribolium castanem, the red flour beetle, is a pest of stored products found worldwide. The Trécé Dome trap acts as a pitfall for beetles and is commercially used in food facilities. Increased capture of T. castaneum has been previously documented when traps already contained conspecifics, but captures did not increase when traps were seeded with  different species. Prior work only examined T. castaneum captured when traps were seeded with 25 dead conspecifics after a 2 h incubation in Trécé Storgard oil. However, density of dead beetles in a trap and time of their incubation in kairomone oil are likely to modulate attraction and affect the subsequent capture of live T. castaneum. Thus, we examined these questions with two strains of T. castaneum, one collected as recently as 2019, in wind tunnel and release-recapture experiments. Volatiles from each trap treatment were also collected using a push headspace collection system and gas chromatography coupled with mass spectrometry. We found that volatile emissions by dead conspecifics changed over different densities and time in traps. However, while the aggregation pheromone of T. castaneum reliably attracted individuals, attraction was not mediated by density of beetles in a trap or time that they had been in the trap. This was true regardless of which T. castaneum strain was used. Our results suggest that while initial studies found elevated attraction to traps with dead conspecifics by T. castaneum, our extensive investigation into this demonstrated that attraction was not as enhanced as first appeared.