Natural-history traits suspected behind interspecific variations of bark- and wood-boring beetles in response to trap size and design

The performances of traps used for pest monitoring are not well understood. Variable trap sizes and shapes make cross-comparisons difficult. We tested with four Scolytinae species (Coleoptera, Curculionidae) a set of traps of the same model (fan-traps) in four sizes (310, 536, 832.5, 1,200 cm²), and a larger trap with another design (a four-vane trap, 4,500 cm²). A significantly linear relationship was observed between trap sizes and catches for Pityogenes chalcographus, but the catches of Ips typographus, Trypodendron lineatum and T. signatum tapered off. In the literature, comparable tapering-off effects were observed with Xyleborus glabratus (Scolytinae) and Agrilus planipennis (Coleoptera, Buprestidae), but a significant linear response with increasing trap size was observed with Trypodendron lineatum and T. rufitarsus. In another test, beetle landing behaviour was measured on a 1 m² glued panel baited with lineatin (the Trypodendron spp. pheromone) and ethanol (a host kairomone). The landing densities of Trypodendron spp. did not increase with the distance to the attractants whilst Anisandrus dispar landed in very significantly higher densities far from the attractants. Species using pheromones to locate mate and host appear to land closer to the source of attractants than species responding to kairomones for locating a suitable host.