The relationship between Nemozoma elongatum (Coleoptera: Trogossitidae) and its primary bark-beetle prey-species

Abstract Key message Nemozoma elongatum (Linnaeus, 1761) shows a positive response to artificially produced lures targeting its two main prey species, Pityogenes chalcographus (Linnaeus, 1761) and Taphrorychus bicolor (Herbst, 1793), with a preference for P. chalcographus . We do not recommend using these lures in traps because they could unintentionally capture N. elongatum . However, these lures could potentially aid in controlling target pests by leveraging allochthonous kairomones to attract predators to areas with higher pest densities. Context Nemozoma elongatum in Central Europe primarily preys on P. chalcographus and T. bicolor , but it can target nearly 40 species of bark beetles. While it responds well to the aggregation pheromone of P. chalcographus , its response to artificial lures for T. bicolor is unknown. Aims The study aimed to confirm if N. elongatum beetles react in the same way to a lure containing bicolorin and Chalcoprax® and if their response to the prey abundance of P. chalcographus parallels the response observed in T. bicolor . Methods During 2022, three Theysohn® pheromone traps were set with Beech Bark Beetle Lure®, containing bicolorin, and one trap with Chalcoprax® in mature beech stands at 11 study sites across the Czech Republic. To study the dependence of the numbers of N. elongatum captured, GLMMs were used to analyze the following variables: both lures, abundance of prey species, abundance of beech, age of beech, altitude, presence of adjacent non-forest areas (such as a freshly exposed edge of a beech forest), and the distances to the nearest spruce forest and the nearest clear-cut area. Results N. elongatum prefers P. chalcographus as its primary prey, as indicated by its response to the tested lures. Its abundance is dependent on the presence of T. bicolor and P. chalcographus . Conclusion N. elongatum is a prey opportunist that responds to bark beetle aggregation pheromones, as confirmed for several species. It is frequently caught in traps with Chalcoprax® and bicolorin, the pheromone of T. bicolor . Although more commonly attracted to Chalcoprax®, indicating a preference for P. chalcographus , N. elongatum may consume other species given its attraction to volatile compounds from host trees.